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IGCSE · 4MA1 · Topic

Vectors: past paper questions & worked solutions

Every Vectors question from the 4MA1 papers in our bank, 2020–2026, sorted from easiest to hardest. Try each one first, then open the worked solution.

28questions
135marks in total
52%of papers (28 of 54) include it
2/5/21easy / medium / hard

Questions, easiest first

Level is estimated from marks: 1–2 easy, 3–4 medium, 5+ hard.

1. Jun 2026 P2HR · Q18

Easy2 marks
Jun 2026 P2HR Question 18 (2 marks): Vectors – 18 Here are two vectors. AB → = 4 5 � �� � �� CB → = � � �� � �� 2 8 Find AC → as a column vector. AC → =     (Total for Question 18 is 2 marks)
Show worked solution
  1. Solution | Step 1
    \[\overrightarrow{AC}=\overrightarrow{AB}+\overrightarrow{BC}=\overrightarrow{AB}-\overrightarrow{CB}.\]

    Reverse CB to travel from B to C.

  2. Solution | Step 2
    \[\overrightarrow{AC}=\begin{pmatrix}4\\5\end{pmatrix}-\begin{pmatrix}-2\\8\end{pmatrix}=\begin{pmatrix}6\\-3\end{pmatrix}.\]

    Subtract corresponding components.

Final answer

\(\overrightarrow{AC}=\begin{pmatrix}6\\-3\end{pmatrix}\).

2. Jan 2021 P1HR · Q13

Easy2 marks
Jan 2021 P1HR Question 13 (2 marks): Vectors – 13 Here are two vectors. AB → = 5 3     CB → = -     2 4 Find, as a column vector, AC →   (Total for Question 13 is 2 marks)
Show worked solution
  1. Use vectors
    \[ \overrightarrow{AB}=\begin{pmatrix}5\\3\end{pmatrix} \]
  2. Use vectors

    and

    \[ \overrightarrow{CB}=\begin{pmatrix}-2\\4\end{pmatrix} \]
  3. Use vectors

    So

    \[ \overrightarrow{BC}=-\overrightarrow{CB} =\begin{pmatrix}2\\-4\end{pmatrix} \]
    \[ \overrightarrow{AC} =\overrightarrow{AB}+\overrightarrow{BC} =\begin{pmatrix}5\\3\end{pmatrix} +\begin{pmatrix}2\\-4\end{pmatrix} =\begin{pmatrix}7\\-1\end{pmatrix} \]
Final answer

\(\begin{pmatrix}7\\-1\end{pmatrix}\).

3. Jun 2025 P2HR · Q18

Medium3 marks
Jun 2025 P2HR Question 18 (3 marks): Vectors – 18 OAB is a triangle. A P 4b 4a B O Diagram NOT accurately drawn = 4a = 4b P is the point on AB such that AP : PB = 1 : 3 (a) Write down in terms of a and b   (1) (b) Express in terms of a and b Give your answer in its s
Show worked solution
  1. Use vectors
    \[ \overrightarrow{AB}=\overrightarrow{OB}-\overrightarrow{OA}=4\mathbf b-4\mathbf a \]
  2. Use vectors

    Since \(AP:PB=1:3\), point \(P\) is one quarter of the way from \(A\) to \(B\).

    \[ \overrightarrow{AP}=\frac14\overrightarrow{AB} =\frac14(4\mathbf b-4\mathbf a) =\mathbf b-\mathbf a \]
    \[ \overrightarrow{OP}=\overrightarrow{OA}+\overrightarrow{AP} =4\mathbf a+\mathbf b-\mathbf a =3\mathbf a+\mathbf b \]
Final answer

\(\overrightarrow{AB}=4\mathbf b-4\mathbf a\), and \(\overrightarrow{OP}=3\mathbf a+\mathbf b\).

4. May 2025 4WM2HR · Q16

Medium3 marks
May 2025 4WM2HR Question 16 (3 marks): Vectors – 16 OAB is a triangle. A P 4b 4a B O Diagram NOT accurately drawn = 4a = 4b P is the point on AB such that AP : PB = 1 : 3 (a) Write down in terms of a and b   (1) (b) Express in terms of a and b Give your answer in its s
Show worked solution
  1. Required

    $\\overrightarrow{OA}=4\\mathbf{a}$, $\\overrightarrow{OB}=4\\mathbf{b}$, AP:PB = 1:3. (a) Find $\\overrightarrow{AB}$. (b) Express $\\overrightarrow{OP}$ in simplest form.

  2. Part (a)

    $$\\overrightarrow{AB} = \\overrightarrow{AO}+\\overrightarrow{OB} = -4\\mathbf{a}+4\\mathbf{b}$$

  3. Answer

    $\\overrightarrow{AB} = 4\\mathbf{b}-4\\mathbf{a}$

  4. AP PB 1 3 means

    AP:PB = 1:3 means $\\overrightarrow{AP} = \\tfrac{1}{4}\\overrightarrow{AB}$: $$\\overrightarrow{AP} = \\tfrac{1}{4}(4\\mathbf{b}-4\\mathbf{a}) = \\mathbf{b}-\\mathbf{a}$$

  5. Use

    Use $\\overrightarrow{OP} = \\overrightarrow{OA}+\\overrightarrow{AP}$: $$\\overrightarrow{OP} = 4\\mathbf{a}+(\\mathbf{b}-\\mathbf{a}) = 3\\mathbf{a}+\\mathbf{b}$$

Final answer

$\\overrightarrow{OP} = 3\\mathbf{a}+\\mathbf{b}$

5. Nov 2024 P2H · Q17

Medium3 marks
Nov 2024 P2H Question 17 (3 marks): Vectors – 17 Here are two vectors.    5 2   4 14 Calculate the magnitude of the vector   (Total for Question 17 is 3 marks)
Show worked solution
  1. Use vectors
    \[ \overrightarrow{GF}=-\overrightarrow{FG} =\begin{pmatrix}5\\-2\end{pmatrix} \]
    \[ \overrightarrow{HF} =\overrightarrow{HG}+\overrightarrow{GF} =\begin{pmatrix}4\\14\end{pmatrix} +\begin{pmatrix}5\\-2\end{pmatrix} =\begin{pmatrix}9\\12\end{pmatrix} \]
  2. Magnitude

    Magnitude:

    \[ |\overrightarrow{HF}|=\sqrt{9^2+12^2}=15 \]
Final answer

\(15\).

6. Jan 2020 P2H · Q23

Medium3 marks
Jan 2020 P2H Question 23 (3 marks): Vectors – 23 Diagram NOT accurately drawn 4a 2b A B C M P ABC is a triangle. The midpoint of BC is M. P is a point on AM. AB → = 4a AC → = 2b AP → = 3 2 a + 3 4 b Find the ratio AP : PM   (Total for Question 23 is 3 marks)
Show worked solution
  1. Split the ratio

    Since \(M\) is the midpoint of \(BC\),

    \[ \overrightarrow{AM}=\frac{\overrightarrow{AB}+\overrightarrow{AC}}{2} \]
    \[ \overrightarrow{AM}=\frac{4a+2b}{2}=2a+b \]
  2. Given
    \[ \overrightarrow{AP}=\frac32a+\frac34b \]
  3. Factorise

    Factorise:

    \[ \overrightarrow{AP}=\frac34(2a+b)=\frac34\overrightarrow{AM} \]
  4. Split the ratio

    So \(AP\) is \(\frac34\) of \(AM\), leaving \(PM\) as \(\frac14\) of \(AM\).

Final answer

\(AP:PM=3:1\)

7. Jun 2026 P2H · Q22

Medium4 marks
Jun 2026 P2H Question 22 (4 marks): Vectors – 22 The diagram shows a quadrilateral OABC where O, A, B and C represent the positions of four houses. Diagram NOT accurately drawn C O A B �� �� � �� 2 8 �� �� � �� 21 14 �� �� � �� 12 3 Ria walks directly from A to B An
Show worked solution
  1. Solution | Step 1
    \[\overrightarrow{AB}=\binom{21}{14}-\binom{2}{8}=\binom{19}{6},\quad \overrightarrow{AC}=\binom{12}{3}-\binom{2}{8}=\binom{10}{-5},\] \[\overrightarrow{CB}=\binom{21}{14}-\binom{12}{3}=\binom{9}{11}.\]

    Subtract the starting position vector from the finishing position vector.

  2. Solution | Step 2
    \[AB=\sqrt{19^2+6^2}=\sqrt{397},\quad AC=\sqrt{10^2+(-5)^2}=\sqrt{125},\quad CB=\sqrt{9^2+11^2}=\sqrt{202}.\]

    The modulus of a two-dimensional vector is the square root of the sum of squares of its components.

  3. Solution | Step 3
    \[\text{Extra distance}=AC+CB-AB=\sqrt{125}+\sqrt{202}-\sqrt{397}=5.468151\ldots\text{ m}.\]

    Compare Anna's two-stage route with Ria's direct route; do not round the intermediate lengths.

Final answer

Anna walks \(5.5\text{ m}\) further (1 decimal place).

8. Jun 2026 4WM2HR · Q18

Hard5 marks
Jun 2026 4WM2HR Question 18 (5 marks): Vectors – 18 Here are two vectors. OA = (4, -3), BA = (-15, 8). (a) Find 2AO as a column vector. (b) Find OB as a column vector. (c) Calculate the magnitude of the vector BA
Show worked solution
  1. (a) Reverse OA and double
    \[\overrightarrow{AO}=\begin{pmatrix}-4\\3\end{pmatrix},\qquad 2\overrightarrow{AO}=\begin{pmatrix}-8\\6\end{pmatrix}\]
  2. (b) Route O → A → B
    \[\overrightarrow{OB}=\overrightarrow{OA}+\overrightarrow{AB}=\begin{pmatrix}4\\-3\end{pmatrix}+\begin{pmatrix}15\\-8\end{pmatrix}=\begin{pmatrix}19\\-11\end{pmatrix}\]
  3. (c) Magnitude
    \[|\overrightarrow{BA}|=\sqrt{(-15)^2+8^2}=\sqrt{289}=17\]
Final answer

(a) \(\begin{pmatrix}-8\\6\end{pmatrix}\) (b) \(\begin{pmatrix}19\\-11\end{pmatrix}\) (c) \(17\)

9. Jun 2025 P1H · Q23

Hard5 marks
Jun 2025 P1H Question 23 (5 marks): Vectors – 23 A P Q O B R Diagram NOT accurately drawn OAB is a triangle. P is the midpoint of OA Q is a point on OB ABR and PQR are straight lines. OA → = 12a OB → = 8b (a) Express AB → in terms of a and b   (1) AB : BR = 1 : 2 OQ
Show worked solution
  1. Use vectors

    For part (a),

    \[ \vec{OA}=12\mathbf a,\qquad \vec{OB}=8\mathbf b \]
    \[ \vec{AB}=\vec{OB}-\vec{OA} \]
    \[ \vec{AB}=8\mathbf b-12\mathbf a \]
  2. Find the midpoint

    For part (b), \(P\) is the midpoint of \(OA\), so

    \[ \vec{OP}=6\mathbf a \]
  3. Given
    \[ AB:BR=1:2 \]
    \[ \vec{BR}=2\vec{AB} \]
    \[ \vec{BR}=16\mathbf b-24\mathbf a \]
  4. Use vectors

    Therefore

    \[ \vec{OR}=\vec{OB}+\vec{BR} \]
    \[ \vec{OR}=8\mathbf b+16\mathbf b-24\mathbf a \]
    \[ \vec{OR}=-24\mathbf a+24\mathbf b \]
  5. Use vectors

    Since \(P,Q,R\) are collinear, write \(Q\) on \(PR\):

    \[ \vec{OQ}=\vec{OP}+t(\vec{OR}-\vec{OP}) \]
    \[ \vec{OQ}=6\mathbf a+t(-30\mathbf a+24\mathbf b) \]
    \[ \vec{OQ}=(6-30t)\mathbf a+24t\mathbf b \]
  6. Use vectors

    But \(Q\) lies on \(OB\), so there is no \(\mathbf a\) component:

    \[ 6-30t=0 \]
    \[ t=\frac15 \]
  7. Use vectors

    Then

    \[ \vec{OQ}=24\left(\frac15\right)\mathbf b \]
    \[ \vec{OQ}=\frac{24}{5}\mathbf b \]
  8. Use vectors

    Since \(\vec{OQ}=n\mathbf b\),

    \[ n=\frac{24}{5} \]
Final answer

\(\vec{AB}=8\mathbf b-12\mathbf a,\quad n=\frac{24}{5}\)

10. May 2025 4WM2H · Q26

Hard5 marks
May 2025 4WM2H Question 26 (5 marks): Vectors – 26 The diagram shows a quadrilateral OPQR in which = 2a = 6c = a + 3c (a) Find in terms of a and c =   (1) The point T is such that = 8c The point X lies on QR such that PXT is a straight line. (b) Using a vector method,
Show worked solution
  1. (a)
    \[ \overrightarrow{QR}=\overrightarrow{OR}-\overrightarrow{OQ} \]
    \[ \overrightarrow{OQ}=2a+(a+3c)=3a+3c \]
    \[ \overrightarrow{QR}=6c-(3a+3c)=3c-3a \]
  2. (b) Let divide so that

    (b) Let \(X\) divide \(QR\) so that

    \[ \overrightarrow{QX}=\lambda\overrightarrow{QR} \]
  3. Calculate value

    Then

    \[ \overrightarrow{OX}=3a+3c+\lambda(3c-3a) \]
  4. Calculate value

    Also \(X\) lies on \(PT\), where \(\overrightarrow{OT}=14c\), so

    \[ \overrightarrow{OX}=2a+\mu(14c-2a) \]
  5. Equating coefficients gives . Therefore

    Equating coefficients gives \(\lambda=\frac59\). Therefore

    \[ QX:XR=\frac59:\frac49=5:4 \]
Final answer

\(\overrightarrow{QR}=3c-3a\); \(QX:XR=5:4\).

11. Nov 2023 P2H · Q22

Hard5 marks
Nov 2023 P2H Question 22 (5 marks): Vectors – 22 P B C A O 3a 4b 2a - 2b Diagram NOT accurately drawn OACB is a quadrilateral. = 3a = 4b = 2a - 2b (a) (i) Find the vector in terms of a and b Simplify your answer. =   (1) (ii) Find the vector in terms of a and b =
Show worked solution
  1. Split the ratio
    \[ \overrightarrow{OA}=3a,\quad \overrightarrow{OB}=4b,\quad \overrightarrow{BC}=2a-2b \]
  2. Part (a)

    Part (a):

    \[ \overrightarrow{OC}=\overrightarrow{OB}+\overrightarrow{BC} =4b+(2a-2b)=2a+2b \]
    \[ \overrightarrow{AB}=\overrightarrow{OB}-\overrightarrow{OA} =4b-3a \]
  3. Split the ratio

    For part (b), let \(P\) divide \(AB\) so that

    \[ \overrightarrow{AP}=\mu\overrightarrow{AB} \]
  4. Split the ratio

    Then

    \[ \overrightarrow{OP}=3a+\mu(4b-3a)=(3-3\mu)a+4\mu b \]
  5. Split the ratio

    Since \(P\) lies on \(OC\), also let

    \[ \overrightarrow{OP}=\lambda(2a+2b) \]
  6. Equating coefficients

    Equating coefficients:

    \[ 3-3\mu=2\lambda,\quad 4\mu=2\lambda \]
  7. Split the ratio

    From \(4\mu=2\lambda\), \(\lambda=2\mu\).

    \[ 3-3\mu=4\mu \]
    \[ \mu=\frac37 \]
  8. Split the ratio

    So \(AP:PB=\frac37:\frac47\).

Final answer

\(\overrightarrow{OC}=2a+2b\), \(\overrightarrow{AB}=4b-3a\), and \(AP:PB=3:4\)

12. May 2023 P1H · Q19

Hard5 marks
May 2023 P1H Question 19 (5 marks): Vectors – 19 A B N O P M a b Diagram NOT accurately drawn OMA, ONB, MPB and NPA are straight lines. M is the midpoint of OA ON : NB = 1 : 5 OM → = a ON → = b (a) Find in terms of a and b the vector AN →   (1) (b) Use a vector meth
Show worked solution
  1. Split the ratio

    Since \(M\) is the midpoint of \(OA\),

    \[ \overrightarrow{OA}=2a \]
  2. Split the ratio

    Also,

    \[ \overrightarrow{ON}=b \]
  3. Split the ratio

    So

    \[ \overrightarrow{AN}=\overrightarrow{ON}-\overrightarrow{OA}=b-2a \]
  4. Let
    \[ \overrightarrow{AP}=\lambda\overrightarrow{AN} \]
  5. Split the ratio

    Then

    \[ \overrightarrow{OP}=2a+\lambda(b-2a)=(2-2\lambda)a+\lambda b \]
  6. Split the ratio

    Since \(ON:NB=1:5\),

    \[ \overrightarrow{OB}=6b \]
  7. Split the ratio

    Point \(P\) is also on \(MB\), so

    \[ \overrightarrow{OP}=a+\mu(6b-a)=(1-\mu)a+6\mu b \]
  8. Compare coefficients

    Compare coefficients:

    \[ 2-2\lambda=1-\mu \]
    \[ \lambda=6\mu \]
  9. Split the ratio

    From \(\mu=2\lambda-1\),

    \[ \lambda=6(2\lambda-1) \]
    \[ 11\lambda=6 \]
    \[ \lambda=\frac6{11} \]
  10. Split the ratio

    So

    \[ AP:PN=\frac6{11}:\frac5{11}=6:5 \]
Final answer

(a) \(b-2a\), (b) \(6:5\)

13. May 2023 P1HR · Q19

Hard5 marks
May 2023 P1HR Question 19 (5 marks): Vectors – 19 The diagram shows a triangle ABC where A, B and C represent the positions of three towns. A C B Diagram NOT accurately drawn AB → = 7 2   BC → =   3 5 Pru travels directly from A to B and then directly from B to
Show worked solution
  1. Pru travels
    \[ |AB|+|BC|=\sqrt{7^2+(-2)^2}+\sqrt{(-3)^2+5^2} \]
    \[ =\sqrt{53}+\sqrt{34}=13.111\ldots \]
  2. Simplify surd

    Yang travels from \(A\) to \(C\).

    \[ \overrightarrow{AC}=\overrightarrow{AB}+\overrightarrow{BC} =\begin{pmatrix}7\\-2\end{pmatrix}+\begin{pmatrix}-3\\5\end{pmatrix} =\begin{pmatrix}4\\3\end{pmatrix} \]
    \[ |AC|=\sqrt{4^2+3^2}=5 \]
  3. Difference

    Difference: \[ 13.111\ldots-5=8.111\ldots \]

Final answer

Pru travels \(8.1\text{ km}\) further.

14. Jun 2022 P2H · Q21

Hard5 marks
Jun 2022 P2H Question 21 (5 marks): Vectors – 21 Diagram NOT accurately drawn O Q B P A 4a 6b OAB is a triangle. Q is the point on AB such that OQP is a straight line. OA → = 4a OB → = 6b AP → = 2a + 8b Using a vector method, find the ratio AQ : QB AQ : QB =   (Tota
Show worked solution
  1. Split the ratio
    \[ \overrightarrow{OA}=4a,\quad \overrightarrow{OB}=6b,\quad \overrightarrow{AP}=2a+8b \]
  2. Split the ratio

    So

    \[ \overrightarrow{OP}=\overrightarrow{OA}+\overrightarrow{AP} =4a+(2a+8b)=6a+8b \]
  3. Split the ratio

    Since \(Q\) lies on \(OP\), let

    \[ \overrightarrow{OQ}=\lambda(6a+8b) \]
  4. Split the ratio

    Since \(Q\) lies on \(AB\), let

    \[ \overrightarrow{OQ}=\overrightarrow{OA}+\mu\overrightarrow{AB} \]
    \[ \overrightarrow{AB}=6b-4a \]
  5. Split the ratio

    So

    \[ \overrightarrow{OQ}=4a+\mu(6b-4a)=(4-4\mu)a+6\mu b \]
  6. Equating coefficients

    Equating coefficients:

    \[ 6\lambda=4-4\mu,\quad 8\lambda=6\mu \]
  7. Split the ratio

    From \(8\lambda=6\mu\), \(\mu=\frac43\lambda\).

    \[ 6\lambda=4-\frac{16}{3}\lambda \]
    \[ 34\lambda=12,\quad \lambda=\frac6{17} \]
    \[ \mu=\frac{8}{17} \]
  8. Split the ratio

    So \(AQ:QB=\frac8{17}:\frac9{17}\).

Final answer

\(AQ:QB=8:9\)

15. Jun 2022 P2HR · Q25

Hard5 marks
Jun 2022 P2HR Question 25 (5 marks): Vectors – 25 ABCD is a parallelogram and ADM is a straight line. Diagram NOT accurately drawn A D K M B L C AB → = a BC → = b DM → = 1 2 b K is the point on AB such that AK : AB = λ : 1 L is the point on CD such that CL : CD = μ :
Show worked solution
  1. Let be the origin

    Let \(A\) be the origin.

    \[ \vec{AB}=\mathbf a,\qquad \vec{BC}=\mathbf b \]
  2. Read the graph

    So

    \[ B=\mathbf a,\qquad D=\mathbf b,\qquad C=\mathbf a+\mathbf b \]
  3. Read the graph

    Also

    \[ \vec{DM}=\frac12\mathbf b \]
  4. Read the graph

    So

    \[ M=\frac32\mathbf b \]
  5. Point is on

    Point \(K\) is on \(AB\):

    \[ K=\lambda\mathbf a \]
  6. Read the graph

    Point \(L\) is on \(CD\), and \(\vec{CD}=-\mathbf a\):

    \[ L=C+\mu(D-C) \]
    \[ L=\mathbf a+\mathbf b+\mu(-\mathbf a) \]
    \[ L=(1-\mu)\mathbf a+\mathbf b \]
  7. Given
    \[ \lambda:\mu=1:2 \]
    \[ \mu=2\lambda \]
  8. Read the graph

    Since \(K,L,M\) are collinear, \(\vec{KM}\) is a multiple of \(\vec{KL}\).

    \[ \vec{KM}=-\lambda\mathbf a+\frac32\mathbf b \]
    \[ \vec{KL}=(1-\mu-\lambda)\mathbf a+\mathbf b \]
    \[ \vec{KL}=(1-3\lambda)\mathbf a+\mathbf b \]
  9. Compare coefficients using
    \[ \vec{KM}=\frac32\vec{KL} \]
    \[ -\lambda=\frac32(1-3\lambda) \]
    \[ -2\lambda=3-9\lambda \]
    \[ 7\lambda=3 \]
    \[ \lambda=\frac37 \]
  10. Read the graph

    Then

    \[ \mu=2\lambda=\frac67 \]
Final answer

\(\displaystyle \lambda=\frac37,\quad \mu=\frac67\)

16. Jan 2022 P1H · Q22

Hard5 marks
Jan 2022 P1H Question 22 (5 marks): Vectors – 22 The diagram shows triangle OAB Diagram NOT accurately drawn A O N B P M OA → = 8a OB → = 6b M is the point on OB such that OM : MB = 1 : 2 N is the midpoint of AB P is the point of intersection of ON and AM Using a ve
Show worked solution
  1. Use vectors
    \[ \vec{OA}=8\mathbf a,\qquad \vec{OB}=6\mathbf b \]
  2. Use vectors

    Since \(OM:MB=1:2\),

    \[ \vec{OM}=\frac13\vec{OB} \]
    \[ \vec{OM}=2\mathbf b \]
  3. Find the midpoint

    Since \(N\) is the midpoint of \(AB\),

    \[ \vec{ON}=\frac{8\mathbf a+6\mathbf b}{2} \]
    \[ \vec{ON}=4\mathbf a+3\mathbf b \]
  4. Use vectors

    Point \(P\) lies on \(ON\), so

    \[ \vec{OP}=\lambda(4\mathbf a+3\mathbf b) \]
  5. Use vectors

    Point \(P\) also lies on \(AM\), so

    \[ \vec{OP}=8\mathbf a+\mu(2\mathbf b-8\mathbf a) \]
    \[ \vec{OP}=(8-8\mu)\mathbf a+2\mu\mathbf b \]
  6. Equate coefficients

    Equate coefficients:

    \[ 4\lambda=8-8\mu \]
    \[ 3\lambda=2\mu \]
  7. Use vectors

    From \(3\lambda=2\mu\),

    \[ \mu=\frac32\lambda \]
  8. Substitute

    Substitute:

    \[ 4\lambda=8-8\left(\frac32\lambda\right) \]
    \[ 4\lambda=8-12\lambda \]
    \[ 16\lambda=8 \]
    \[ \lambda=\frac12 \]
  9. Use vectors

    Therefore

    \[ \vec{OP}=\frac12(4\mathbf a+3\mathbf b) \]
    \[ \vec{OP}=2\mathbf a+\frac32\mathbf b \]
Final answer

\(\displaystyle \vec{OP}=2\mathbf a+\frac32\mathbf b\)

17. Jan 2022 P1HR · Q24

Hard5 marks
Jan 2022 P1HR Question 24 (5 marks): Vectors – 24 OXYZ is a trapezium. X M O Y Z N Diagram NOT accurately drawn OX = a XY = b OZ = 3b M is the midpoint of OX N is the point such that MNZ and ONY are straight lines. Given that ON : OY = λ : 1 use a vector method to fi
Show worked solution
  1. Take as the origin

    Take \(O\) as the origin.

    \[ \vec{OX}=\mathbf a,\qquad \vec{XY}=\mathbf b,\qquad \vec{OZ}=3\mathbf b \]
  2. Use vectors

    So

    \[ \vec{OY}=\mathbf a+\mathbf b \]
  3. Find the midpoint

    Since \(M\) is the midpoint of \(OX\),

    \[ \vec{OM}=\frac12\mathbf a \]
  4. Use vectors

    Given \(ON:OY=\lambda:1\),

    \[ \vec{ON}=\lambda(\mathbf a+\mathbf b) \]
  5. Use vectors

    Point \(N\) also lies on \(MZ\), so

    \[ \vec{ON}=\frac12\mathbf a+t\left(3\mathbf b-\frac12\mathbf a\right) \]
    \[ \vec{ON}=\left(\frac12-\frac{t}{2}\right)\mathbf a+3t\mathbf b \]
  6. Use vectors

    Equate coefficients with \(\lambda\mathbf a+\lambda\mathbf b\):

    \[ \lambda=\frac12-\frac{t}{2} \]
    \[ \lambda=3t \]
  7. Use vectors

    So

    \[ t=\frac{\lambda}{3} \]
  8. Substitute

    Substitute:

    \[ \lambda=\frac12-\frac{1}{2}\left(\frac{\lambda}{3}\right) \]
    \[ \lambda=\frac12-\frac{\lambda}{6} \]
    \[ \frac76\lambda=\frac12 \]
    \[ \lambda=\frac37 \]
Final answer

\(\displaystyle \lambda=\frac37\)

18. May 2021 P1H · Q26

Hard5 marks
May 2021 P1H Question 26 (5 marks): Vectors – 26 OACB is a trapezium. A P B O 3b C Diagram NOT accurately drawn 2a 5b OA → = 2a OB → = 5b AC → = 3b The diagonals, OC and AB, of the trapezium intersect at the point P. Find and simplify an expression, in terms of a an
Show worked solution
  1. Use vectors
    \[ \overrightarrow{OA}=2\mathbf a,\qquad \overrightarrow{OB}=5\mathbf b,\qquad \overrightarrow{AC}=3\mathbf b \]
  2. Use vectors

    So

    \[ \overrightarrow{OC} =\overrightarrow{OA}+\overrightarrow{AC} =2\mathbf a+3\mathbf b \]
  3. Use vectors

    Since \(P\) lies on \(OC\), let

    \[ \overrightarrow{OP}=t(2\mathbf a+3\mathbf b) \]
  4. Use vectors

    Since \(P\) also lies on \(AB\), let

    \[ \overrightarrow{OP} =\overrightarrow{OA}+s\overrightarrow{AB} \]
  5. Use vectors

    Now

    \[ \overrightarrow{AB} =\overrightarrow{OB}-\overrightarrow{OA} =5\mathbf b-2\mathbf a \]
  6. Use vectors

    So

    \[ \overrightarrow{OP} =2\mathbf a+s(5\mathbf b-2\mathbf a) \]
    \[ \overrightarrow{OP} =(2-2s)\mathbf a+5s\mathbf b \]
  7. Use vectors

    Compare this with

    \[ t(2\mathbf a+3\mathbf b)=2t\mathbf a+3t\mathbf b \]
  8. Equating coefficients

    Equating coefficients:

    \[ 2t=2-2s \]
    \[ 3t=5s \]
  9. Use vectors

    From \(t=1-s\),

    \[ 3(1-s)=5s \]
    \[ 3=8s \]
    \[ s=\frac{3}{8} \]
  10. Use vectors

    So

    \[ t=1-\frac{3}{8}=\frac{5}{8} \]
  11. Use vectors

    Therefore

    \[ \overrightarrow{OP} =\frac{5}{8}(2\mathbf a+3\mathbf b) \]
    \[ \overrightarrow{OP} =\frac{5}{4}\mathbf a+\frac{15}{8}\mathbf b \]
Final answer

\(\boxed{\frac{5}{4}\mathbf a+\frac{15}{8}\mathbf b}\)

19. Jan 2020 P2HR · Q26

Hard5 marks
Jan 2020 P2HR Question 26 (5 marks): Vectors – 26 The diagram shows trapezium OACB. Diagram NOT accurately drawn A B C O 4b 6b 3a OA → = 3a OB → = 6b AC → = 4b N is the point on OC such that ANB is a straight line. Find ON → as a simplified expression in terms of a a
Show worked solution
  1. Read the graph
    \[ \vec{OA}=3\mathbf a,\qquad \vec{OB}=6\mathbf b,\qquad \vec{AC}=4\mathbf b \]
  2. Read the graph

    So

    \[ \vec{OC}=3\mathbf a+4\mathbf b \]
  3. Read the graph

    Point \(N\) lies on \(OC\), so

    \[ \vec{ON}=t(3\mathbf a+4\mathbf b) \]
  4. Read the graph

    Point \(N\) also lies on \(AB\), so

    \[ \vec{ON}=3\mathbf a+s(6\mathbf b-3\mathbf a) \]
    \[ \vec{ON}=(3-3s)\mathbf a+6s\mathbf b \]
  5. Equate coefficients

    Equate coefficients:

    \[ 3t=3-3s \]
    \[ 4t=6s \]
  6. Read the graph

    So

    \[ t=1-s \]
  7. Read the graph

    and

    \[ t=\frac32s \]
    \[ \frac32s=1-s \]
    \[ 5s=2 \]
    \[ s=\frac25 \]
  8. Read the graph

    Then

    \[ t=\frac35 \]
  9. Read the graph

    Therefore

    \[ \vec{ON}=\frac35(3\mathbf a+4\mathbf b) \]
    \[ \vec{ON}=\frac95\mathbf a+\frac{12}{5}\mathbf b \]
Final answer

\(\displaystyle \vec{ON}=\frac95\mathbf a+\frac{12}{5}\mathbf b\)

20. Specimen 4WM2H · Q23

Hard5 marks
Specimen 4WM2H Question 23 (5 marks): Vectors – 23 OAB is a triangle. Q is on AB and OQP is a straight line. Vector OA = 4a, vector OB = 6b and vector AP = 2a + 8b. Using a vector method, find the ratio AQ : QB. (Total for Question 23 is 5 marks)
Show worked solution
  1. Use vectors
    \[ \overrightarrow{OA}=4a,\qquad \overrightarrow{OB}=6b,\qquad \overrightarrow{AP}=2a+8b \]
  2. Use vectors

    So

    \[ \overrightarrow{OP}=\overrightarrow{OA}+\overrightarrow{AP} \]
    \[ \overrightarrow{OP}=4a+(2a+8b)=6a+8b \]
  3. Use vectors

    Since \(O,Q,P\) are collinear, let

    \[ \overrightarrow{OQ}=\lambda(6a+8b) \]
  4. Use vectors

    Also \(Q\) lies on \(AB\). Let

    \[ \overrightarrow{AQ}=\mu\overrightarrow{AB} \]
  5. Use vectors

    Then

    \[ \overrightarrow{AB}=6b-4a \]
    \[ \overrightarrow{OQ}=4a+\mu(6b-4a) \]
    \[ \overrightarrow{OQ}=(4-4\mu)a+6\mu b \]
  6. Use vectors

    Compare coefficients with

    \[ \lambda(6a+8b)=6\lambda a+8\lambda b \]
  7. Use vectors

    So

    \[ 4-4\mu=6\lambda,\qquad 6\mu=8\lambda \]
  8. Use vectors

    From \(6\mu=8\lambda\),

    \[ \lambda=\frac34\mu \]
  9. Substitute

    Substitute:

    \[ 4-4\mu=6\left(\frac34\mu\right) \]
    \[ 4-4\mu=\frac92\mu \]
    \[ 8=17\mu \]
    \[ \mu=\frac8{17} \]
  10. Use vectors

    Therefore

    \[ AQ:QB=\frac8{17}:\frac9{17}=8:9 \]
Final answer

\(AQ:QB=8:9\).

21. Jun 2026 P1HR · Q25

Hard6 marks
Jun 2026 P1HR Question 25 (6 marks): Vectors – 25 A C D P B O 4b 3a 2a + 2b Diagram NOT accurately drawn OA → = 3a OB → = 4b AC → = 2a + 2b CD → = 3 2 × AC → P is the point on BC such that OPD is a straight line. (a) Find OD → in terms of a and b Give your answer in
Show worked solution
  1. Part (a) | Step 1
    \[\overrightarrow{CD}=\frac32(2\mathbf a+2\mathbf b)=3\mathbf a+3\mathbf b.\]

    Use the stated relationship between CD and AC.

  2. Part (a) | Step 2
    \[\overrightarrow{OD}=\overrightarrow{OA}+\overrightarrow{AC}+\overrightarrow{CD}=3\mathbf a+(2\mathbf a+2\mathbf b)+(3\mathbf a+3\mathbf b)=8\mathbf a+5\mathbf b.\]

    Add consecutive vectors along the route O-A-C-D.

  3. Part (b) | Step 1
    \[\overrightarrow{OC}=3\mathbf a+(2\mathbf a+2\mathbf b)=5\mathbf a+2\mathbf b,\qquad\overrightarrow{BC}=5\mathbf a-2\mathbf b.\]

    Use OC=OA+AC and BC=OC-OB.

  4. Part (b) | Step 2

    Write \(\overrightarrow{OP}=t\overrightarrow{OD}=8t\mathbf a+5t\mathbf b\). Also, because P lies on BC, \[\overrightarrow{OP}=\overrightarrow{OB}+s\overrightarrow{BC}=5s\mathbf a+(4-2s)\mathbf b.\]

    Use one scalar parameter on each of the two intersecting lines.

  5. Part (b) | Step 3
    \[8t=5s,\qquad5t=4-2s,\qquad s=\frac85t.\]

    Equate the coefficients of the two nonparallel base vectors.

  6. Part (b) | Step 4
    \[5t=4-\frac{16}{5}t\quad\Longrightarrow\quad41t=20\quad\Longrightarrow\quad t=\frac{20}{41}.\]

    Substitute the first relation into the second and solve.

  7. Part (b) | Step 5
    \[OP:PD=t:(1-t)=\frac{20}{41}:\frac{21}{41}=20:21.\]

    OD is divided into the fractions t and 1-t at P.

Final answer

(a) \(\overrightarrow{OD}=8\mathbf a+5\mathbf b\)

(b) \(OP:PD=20:21\)

22. Nov 2025 4WM2H · Q24

Hard6 marks
Nov 2025 4WM2H Question 24 (6 marks): Vectors – 24 The diagram shows a quadrilateral OABC A 2a + 4b 5a 10b B P C O Diagram NOT accurately drawn = 5a = 10b 2 4 a b (a) Find in terms of a and b =   (1) (b) Find in terms of a and b Give your answer in its simplest form.
Show worked solution
  1. (a) Find $\\overrightarrow{AC}$

    $$\\overrightarrow{AC} = \\overrightarrow{AO} + \\overrightarrow{OC} = -\\overrightarrow{OA} + \\overrightarrow{OC} = -5\\mathbf{a} + 10\\mathbf{b}$$

  2. Answer

    \(a\)  − 5**a** + 10**b**

  3. (b) Find $\\overrightarrow{OB}$

    $$\\overrightarrow{OB} = \\overrightarrow{OA} + \\overrightarrow{AB} = 5\\mathbf{a} + (2\\mathbf{a} + 4\\mathbf{b}) = 7\\mathbf{a} + 4\\mathbf{b}$$

  4. Answer

    \(b\) 7**a** + 4**b**

    **Step 1: Set up vector equations for $\\overrightarrow{OP}$.** Since *O**P**B* is a straight line, $\\overrightarrow{OP}$ is a scalar multiple of $\\overrightarrow{OB}$. Let this be *λ*. $$\\overrightarrow{OP} = \\lambda(7\\mathbf{a} + 4\\mathbf{b}) = 7\\lambda\\mathbf{a} + 4\\lambda\\mathbf{b}$$

    Since *P* lies on the straight line *A**C*, $\\overrightarrow{AP} = \\mu\\overrightarrow{AC}$ for some scalar *μ*. $$\\overrightarrow{OP} = \\overrightarrow{OA} + \\overrightarrow{AP} = 5\\mathbf{a} + \\mu(-5\\mathbf{a} + 10\\mathbf{b})$$ $$\\overrightarrow{OP} = (5 - 5\\mu)\\mathbf{a} + 10\\mu\\mathbf{b}$$

    **Step 2: Equate the coefficients of **a** and **b**.** 7*λ* = 5 − 5*μ*  — (1) $$4\\lambda = 10\\mu \\implies \\mu = \\frac{4}{10}\\lambda = 0.4\\lambda \\quad \\text{--- (2)}$$

    **Step 3: Solve for *λ*.** Substitute (2) into (1): 7*λ* = 5 − 5(0.4*λ*) 7*λ* = 5 − 2*λ* $$9\\lambda = 5 \\implies \\lambda = \\frac{5}{9}$$

  5. Evaluate fraction

    $$\\overrightarrow{OP} = \\frac{5}{9}(7\\mathbf{a} + 4\\mathbf{b}) = \\frac{35}{9}\\mathbf{a} + \\frac{20}{9}\\mathbf{b}$$

Final answer

$\\frac{35}{9}\\mathbf{a} + \\frac{20}{9}\\mathbf{b}$

23. Nov 2025 P1H · Q27

Hard6 marks
Nov 2025 P1H Question 27 (6 marks): Vectors – 27 A O C D B P 2a 5b - 3a 4b - a Diagram NOT accurately drawn OABC is a quadrilateral. ABP and ODP are straight lines. OA → = 2a AB → = 4b - a OC → = 5b - 3a (a) Find an expression in terms of a and b for the vector BC →
Show worked solution
  1. Read the graph
    \[ \vec{OA}=2\mathbf a,\qquad \vec{AB}=4\mathbf b-\mathbf a,\qquad \vec{OC}=5\mathbf b-3\mathbf a \]
  2. Read the graph

    First find \(\vec{OB}\):

    \[ \vec{OB}=\vec{OA}+\vec{AB} \]
    \[ \vec{OB}=2\mathbf a+4\mathbf b-\mathbf a \]
    \[ \vec{OB}=\mathbf a+4\mathbf b \]
  3. Read the graph

    For part (a),

    \[ \vec{BC}=\vec{OC}-\vec{OB} \]
    \[ \vec{BC}=(5\mathbf b-3\mathbf a)-(\mathbf a+4\mathbf b) \]
    \[ \vec{BC}=\mathbf b-4\mathbf a \]
  4. Read the graph

    For part (b), \(BD:DC=1:3\), so

    \[ \vec{OD}=\vec{OB}+\frac14\vec{BC} \]
    \[ \vec{OD}=\mathbf a+4\mathbf b+\frac14(\mathbf b-4\mathbf a) \]
    \[ \vec{OD}=\frac{17}{4}\mathbf b \]
  5. Read the graph

    Since \(A,B,P\) are collinear, let

    \[ \vec{OP}=\vec{OA}+s\vec{AB} \]
    \[ \vec{OP}=2\mathbf a+s(4\mathbf b-\mathbf a) \]
    \[ \vec{OP}=(2-s)\mathbf a+4s\mathbf b \]
  6. Read the graph

    But \(O,D,P\) are collinear, and \(\vec{OD}\) has only a \(\mathbf b\) component.

  7. Read the graph

    So

    \[ 2-s=0 \]
    \[ s=2 \]
  8. Read the graph

    Then

    \[ \vec{OP}=8\mathbf b \]
  9. Given
    \[ \vec{OP}=n\vec{OD} \]
    \[ 8\mathbf b=n\left(\frac{17}{4}\mathbf b\right) \]
    \[ n=\frac{32}{17} \]
Final answer

\(\vec{BC}=\mathbf b-4\mathbf a,\quad \displaystyle n=\frac{32}{17}\)

24. Nov 2024 P1H · Q24

Hard6 marks
Nov 2024 P1H Question 24 (6 marks): Vectors – 24 OAB is a triangle. Diagram NOT accurately drawn A P R Q O B = 10a = 10b ARQ and ORP are straight lines. = 1 4 and = 1 5 Write the following vectors in terms of a and b Simplify your answers. (i)   (1) (ii)   (1) (iii)
Show worked solution
  1. Read the graph
    \[ \vec{OA}=10\mathbf a,\qquad \vec{OB}=10\mathbf b \]
  2. Read the graph

    Also,

    \[ \vec{AP}=\frac14\vec{AB} \]
  3. Read the graph

    and

    \[ \vec{OQ}=\frac15\vec{OB} \]
  4. Read the graph

    For part (i),

    \[ \vec{OQ}=2\mathbf b \]
    \[ \vec{AQ}=\vec{OQ}-\vec{OA} \]
    \[ \vec{AQ}=2\mathbf b-10\mathbf a \]
  5. Read the graph

    For part (ii),

    \[ \vec{AB}=10\mathbf b-10\mathbf a \]
    \[ \vec{AP}=\frac14(10\mathbf b-10\mathbf a) \]
    \[ \vec{AP}=\frac52\mathbf b-\frac52\mathbf a \]
    \[ \vec{OP}=\vec{OA}+\vec{AP} \]
    \[ \vec{OP}=10\mathbf a-\frac52\mathbf a+\frac52\mathbf b \]
    \[ \vec{OP}=\frac{15}{2}\mathbf a+\frac52\mathbf b \]
  6. Read the graph

    For part (iii), \(R\) lies on \(OP\), so

    \[ \vec{OR}=t\vec{OP} \]
  7. Read the graph

    It also lies on \(AQ\), so

    \[ \vec{OR}=\vec{OA}+s\vec{AQ} \]
    \[ \vec{OR}=10\mathbf a+s(2\mathbf b-10\mathbf a) \]
    \[ \vec{OR}=(10-10s)\mathbf a+2s\mathbf b \]
  8. Read the graph

    Equate with

    \[ t\left(\frac{15}{2}\mathbf a+\frac52\mathbf b\right) \]
    \[ \frac{15}{2}t=10-10s \]
    \[ \frac52t=2s \]
  9. Solve equation

    From the second equation,

    \[ s=\frac54t \]
  10. Substitute

    Substitute:

    \[ \frac{15}{2}t=10-\frac{25}{2}t \]
    \[ 20t=10 \]
    \[ t=\frac12 \]
  11. Read the graph

    So

    \[ \vec{OR}=\frac12\vec{OP} \]
    \[ \vec{OR}=\frac{15}{4}\mathbf a+\frac54\mathbf b \]
Final answer

\(\vec{AQ}=2\mathbf b-10\mathbf a\), \(\displaystyle \vec{OP}=\frac{15}{2}\mathbf a+\frac52\mathbf b\), \(\displaystyle \vec{OR}=\frac{15}{4}\mathbf a+\frac54\mathbf b\)

25. Jun 2024 P2H · Q24

Hard6 marks
Jun 2024 P2H Question 24 (6 marks): Vectors – 24 A B C O P 4a 2a + b 3b Diagram NOT accurately drawn The diagram shows a quadrilateral OACB in which OA → = 4a OB → = 3b BC → = 2a + b (a) Find AC → in terms of a and b Give your answer in its simplest form. AC → =   (
Show worked solution
  1. Read the graph
    \[ \vec{OA}=4\mathbf a,\qquad \vec{OB}=3\mathbf b,\qquad \vec{BC}=2\mathbf a+\mathbf b \]
  2. Read the graph

    So

    \[ \vec{OC}=\vec{OB}+\vec{BC} \]
    \[ \vec{OC}=2\mathbf a+4\mathbf b \]
  3. Read the graph

    For part (a),

    \[ \vec{AC}=\vec{OC}-\vec{OA} \]
    \[ \vec{AC}=(2\mathbf a+4\mathbf b)-4\mathbf a \]
    \[ \vec{AC}=4\mathbf b-2\mathbf a \]
  4. Read the graph

    For part (b), \(AP:PC=3:2\), so

    \[ \vec{OP}=\vec{OA}+\frac35\vec{AC} \]
    \[ \vec{OP}=4\mathbf a+\frac35(4\mathbf b-2\mathbf a) \]
    \[ \vec{OP}=\frac{14}{5}\mathbf a+\frac{12}{5}\mathbf b \]
  5. Read the graph

    Since \(O,P,Q\) are collinear,

    \[ \vec{OQ}=t\vec{OP} \]
    \[ \vec{OQ}=t\left(\frac{14}{5}\mathbf a+\frac{12}{5}\mathbf b\right) \]
  6. Read the graph

    Since \(B,C,Q\) are collinear,

    \[ \vec{OQ}=\vec{OB}+s\vec{BC} \]
    \[ \vec{OQ}=3\mathbf b+s(2\mathbf a+\mathbf b) \]
    \[ \vec{OQ}=2s\mathbf a+(3+s)\mathbf b \]
  7. Equate coefficients

    Equate coefficients:

    \[ \frac{14}{5}t=2s \]
    \[ \frac{12}{5}t=3+s \]
  8. Solve equation

    From the first equation,

    \[ s=\frac75t \]
  9. Substitute into the second

    Substitute into the second:

    \[ \frac{12}{5}t=3+\frac75t \]
    \[ t=3 \]
  10. Read the graph

    Therefore

    \[ \vec{OQ}=3\vec{OP} \]
    \[ \vec{OQ}=\frac{42}{5}\mathbf a+\frac{36}{5}\mathbf b \]
Final answer

\(\vec{AC}=4\mathbf b-2\mathbf a\), \(\displaystyle \vec{OQ}=\frac{42}{5}\mathbf a+\frac{36}{5}\mathbf b\)

26. Jun 2024 P2HR · Q25

Hard6 marks
Jun 2024 P2HR Question 25 (6 marks): Vectors – 25 OPQR is a parallelogram. Diagram NOT accurately drawn Q N R M P O Y OP → = 2a and OR → = 3b The point M lies on PQ such that PM PQ = 1 4 The point N lies on RQ such that RN RQ = 4 5 (a) Find, in terms of a and b, givi
Show worked solution
  1. Calculate value
    \[ \overrightarrow{OP}=2a,\qquad \overrightarrow{OR}=3b \]
  2. Calculate value

    So

    \[ \overrightarrow{OQ}=2a+3b \]
  3. Evaluate fraction

    Since \(PM:PQ=1:4\),

    \[ \overrightarrow{PM}=\frac14\overrightarrow{PQ} \]
    \[ \overrightarrow{PM}=\frac14(3b)=\frac34b \]
    \[ \overrightarrow{OM}=2a+\frac34b \]
  4. Evaluate fraction

    Since \(RN:RQ=4:5\),

    \[ \overrightarrow{RN}=\frac45\overrightarrow{RQ} \]
    \[ \overrightarrow{RN}=\frac45(2a)=\frac85a \]
    \[ \overrightarrow{ON}=3b+\frac85a \]
  5. Evaluate fraction

    So

    \[ \overrightarrow{MR}=\overrightarrow{OR}-\overrightarrow{OM} \]
    \[ \overrightarrow{MR}=3b-\left(2a+\frac34b\right) \]
    \[ \overrightarrow{MR}=-2a+\frac94b \]
  6. Let be on

    Let \(Y\) be on \(ON\), so

    \[ \overrightarrow{OY}=k\overrightarrow{ON} =k\left(\frac85a+3b\right) \]
  7. Evaluate fraction

    Also \(Y\) is on \(MR\), so

    \[ \overrightarrow{OY}=\overrightarrow{OM}+t\overrightarrow{MR} \]
    \[ \overrightarrow{OY}=2a+\frac34b+t\left(-2a+\frac94b\right) \]
  8. Evaluate fraction

    Compare coefficients of \(a\) and \(b\):

    \[ \frac85k=2-2t \]
    \[ 3k=\frac34+\frac94t \]
  9. Solve equation

    From the first equation,

    \[ t=1-\frac45k \]
  10. Substitute into the second equation

    Substitute into the second equation:

    \[ 3k=\frac34+\frac94\left(1-\frac45k\right) \]
    \[ 3k=3-\frac95k \]
    \[ \frac{24}{5}k=3 \]
    \[ k=\frac58 \]
Final answer

\(\overrightarrow{ON}=\frac85a+3b\), \(\overrightarrow{MR}=-2a+\frac94b\), and \(k=\frac58\)

27. Jan 2021 P1H · Q23

Hard6 marks
Jan 2021 P1H Question 23 (6 marks): Vectors – 23 OAB is a triangle. A B O P M N Diagram NOT accurately drawn OA → = 2a and OB → = 2b M is the midpoint of AB. N is the point on OB such that ON : NB = 2 : 1 P is the point on AN such that OPM is a straight line. Use a
Show worked solution
  1. Use vectors
    \[ \vec{OA}=2\mathbf a,\qquad \vec{OB}=2\mathbf b \]
  2. Find the midpoint

    Since \(M\) is the midpoint of \(AB\),

    \[ \vec{OM}=\frac{2\mathbf a+2\mathbf b}{2} \]
    \[ \vec{OM}=\mathbf a+\mathbf b \]
  3. Use vectors

    Since \(ON:NB=2:1\),

    \[ \vec{ON}=\frac23\vec{OB} \]
    \[ \vec{ON}=\frac23(2\mathbf b)=\frac43\mathbf b \]
  4. Use vectors

    Point \(P\) lies on \(OM\), so

    \[ \vec{OP}=t(\mathbf a+\mathbf b) \]
  5. Use vectors

    Point \(P\) also lies on \(AN\), so

    \[ \vec{OP}=2\mathbf a+s\left(\frac43\mathbf b-2\mathbf a\right) \]
    \[ \vec{OP}=(2-2s)\mathbf a+\frac{4s}{3}\mathbf b \]
  6. Use vectors

    Equate coefficients of \(\mathbf a\) and \(\mathbf b\):

    \[ t=2-2s \]
    \[ t=\frac{4s}{3} \]
  7. Use vectors

    So

    \[ \frac{4s}{3}=2-2s \]
    \[ 4s=6-6s \]
    \[ 10s=6 \]
    \[ s=\frac35 \]
  8. Use vectors

    Then

    \[ t=\frac{4}{5} \]
  9. Use vectors

    So \(P\) is \(\frac45\) of the way from \(O\) to \(M\).

Final answer

\(\displaystyle OP:PM=4:1\)

28. Nov 2021 P1H · Q14

Hard8 marks
Nov 2021 P1H Question 14 (8 marks): Vectors – 14 ABCDEF and GHIJKL are regular hexagons each with centre O. Diagram NOT accurately drawn G L I H K J E D A B F C O a b GHIJKL is an enlargement of ABCDEF, with centre O and scale factor 2 OA → = a OB → = b (a) Write th
Show worked solution
  1. Use vectors
    \[ \overrightarrow{OA}=\mathbf a,\qquad \overrightarrow{OB}=\mathbf b \]
  2. (a)(i)
    \[ \overrightarrow{AB}=\overrightarrow{OB}-\overrightarrow{OA} =\mathbf b-\mathbf a \]
  3. Use vectors

    For a regular hexagon,

    \[ \overrightarrow{OC}=\mathbf b-\mathbf a,\quad \overrightarrow{OD}=-\mathbf a,\quad \overrightarrow{OE}=-\mathbf b,\quad \overrightarrow{OF}=\mathbf a-\mathbf b \]
  4. The outer hexagon has scale

    The outer hexagon has scale factor \(2\), so

    \[ \overrightarrow{OI}=2(\mathbf b-\mathbf a),\quad \overrightarrow{OK}=-2\mathbf b,\quad \overrightarrow{OL}=2(\mathbf a-\mathbf b) \]
  5. (ii)
    \[ \overrightarrow{KI} =\overrightarrow{OI}-\overrightarrow{OK} =2(\mathbf b-\mathbf a)-(-2\mathbf b) =4\mathbf b-2\mathbf a \]
  6. (iii)
    \[ \overrightarrow{LD} =\overrightarrow{OD}-\overrightarrow{OL} =-\mathbf a-2(\mathbf a-\mathbf b) =2\mathbf b-3\mathbf a \]
  7. (b) The inner hexagon is

    (b) The inner hexagon is made from 6 equal triangles like \(OAB\):

    \[ \text{inner area}=6\times 5=30 \]
  8. The outer hexagon is an

    The outer hexagon is an enlargement with scale factor \(2\), so area scale factor is \(2^2=4\):

    \[ \text{outer area}=4\times 30=120 \]
    \[ \text{shaded area}=120-30=90 \]
Final answer

(i) \(\mathbf b-\mathbf a\), (ii) \(4\mathbf b-2\mathbf a\), (iii) \(2\mathbf b-3\mathbf a\), (b) \(90\text{ cm}^2\).

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Dr Eslam Ahmed
Dr Eslam Ahmed

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