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O Level Elementary Mathematics Vectors Matrices Quiz

Free O Level E Maths Vectors Matrices quiz, Qwen3.6 Exam version, with questions, answers, and O Level-style practice for Singapore students.

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O Level Elementary Mathematics From Real Exams Generated by Qwen3.6 Plus Updated 2026-08-17

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Answers

O-Level Elementary Mathematics Quiz - Vectors Matrices (Answer Key)

1. a+b=(32)+(15)=(23)\mathbf{a} + \mathbf{b} = \begin{pmatrix} 3 \\ -2 \end{pmatrix} + \begin{pmatrix} -1 \\ 5 \end{pmatrix} = \begin{pmatrix} 2 \\ 3 \end{pmatrix}
[1]

2. 2ab=2(32)(15)=(64)(15)=(79)2\mathbf{a} - \mathbf{b} = 2\begin{pmatrix} 3 \\ -2 \end{pmatrix} - \begin{pmatrix} -1 \\ 5 \end{pmatrix} = \begin{pmatrix} 6 \\ -4 \end{pmatrix} - \begin{pmatrix} -1 \\ 5 \end{pmatrix} = \begin{pmatrix} 7 \\ -9 \end{pmatrix}
[2] (1 for substitution, 1 for answer)

3. a=32+(2)2=9+4=13|\mathbf{a}| = \sqrt{3^2 + (-2)^2} = \sqrt{9+4} = \sqrt{13}.
Unit vector = 113(32)\frac{1}{\sqrt{13}}\begin{pmatrix} 3 \\ -2 \end{pmatrix} or (313213)\begin{pmatrix} \frac{3}{\sqrt{13}} \\ \frac{-2}{\sqrt{13}} \end{pmatrix}.
[2] (1 for magnitude, 1 for unit vector)

4. p=42+(3)2=16+9=25=5|\mathbf{p}| = \sqrt{4^2 + (-3)^2} = \sqrt{16+9} = \sqrt{25} = 5.
[1]

5. kp+q=k(43)+(12)=(4k+13k+2)k\mathbf{p} + \mathbf{q} = k\begin{pmatrix} 4 \\ -3 \end{pmatrix} + \begin{pmatrix} 1 \\ 2 \end{pmatrix} = \begin{pmatrix} 4k+1 \\ -3k+2 \end{pmatrix}.
For parallel to (74)\begin{pmatrix} 7 \\ -4 \end{pmatrix}, gradients must be equal:
3k+24k+1=47\frac{-3k+2}{4k+1} = \frac{-4}{7}
7(3k+2)=4(4k+1)7(-3k+2) = -4(4k+1)
21k+14=16k4-21k + 14 = -16k - 4
18=5k    k=18518 = 5k \implies k = \frac{18}{5} or 3.63.6.
[3] (1 for vector expression, 1 for setting up proportion/equation, 1 for answer)

6. OB=OA+AB\vec{OB} = \vec{OA} + \vec{AB}. Since OABCOABC is a parallelogram, AB=OC=c\vec{AB} = \vec{OC} = \mathbf{c}.
OB=a+c\vec{OB} = \mathbf{a} + \mathbf{c}.
[1]

7. CM=CO+OA+AM\vec{CM} = \vec{CO} + \vec{OA} + \vec{AM}.
CO=c\vec{CO} = -\mathbf{c}.
OA=a\vec{OA} = \mathbf{a}.
MM is midpoint of ABAB, so AM=12AB=12c\vec{AM} = \frac{1}{2}\vec{AB} = \frac{1}{2}\mathbf{c}.
CM=c+a+12c=a12c\vec{CM} = -\mathbf{c} + \mathbf{a} + \frac{1}{2}\mathbf{c} = \mathbf{a} - \frac{1}{2}\mathbf{c}.
[2] (1 for path/method, 1 for simplified answer)

8. AM=12AB=12c\vec{AM} = \frac{1}{2}\vec{AB} = \frac{1}{2}\mathbf{c}.
[1]

9. AB=ba=(5231)=(32)\vec{AB} = \mathbf{b} - \mathbf{a} = \begin{pmatrix} 5-2 \\ 3-1 \end{pmatrix} = \begin{pmatrix} 3 \\ 2 \end{pmatrix}.
BC=cb=(8553)=(32)\vec{BC} = \mathbf{c} - \mathbf{b} = \begin{pmatrix} 8-5 \\ 5-3 \end{pmatrix} = \begin{pmatrix} 3 \\ 2 \end{pmatrix}.
[2]

10. Since AB=BC\vec{AB} = \vec{BC}, the vectors are parallel and share a common point BB. Therefore, A,B,CA, B, C are collinear.
Since the vectors are equal in magnitude, AB=BCAB = BC.
Ratio AB:BC=1:1AB : BC = 1 : 1.
[3] (1 for collinearity reasoning, 1 for ratio logic, 1 for final ratio)

11. OP:PA=1:2    OP=13OAOP : PA = 1 : 2 \implies OP = \frac{1}{3}OA.
OP=13a\vec{OP} = \frac{1}{3}\mathbf{a}.
[1]

12. QQ is midpoint of ABAB. OQ=12(OA+OB)=12(a+b)\vec{OQ} = \frac{1}{2}(\vec{OA} + \vec{OB}) = \frac{1}{2}(\mathbf{a} + \mathbf{b}).
[2]

13. PQ=OQOP=12(a+b)13a\vec{PQ} = \vec{OQ} - \vec{OP} = \frac{1}{2}(\mathbf{a} + \mathbf{b}) - \frac{1}{3}\mathbf{a}.
PQ=(1213)a+12b=16a+12b\vec{PQ} = (\frac{1}{2} - \frac{1}{3})\mathbf{a} + \frac{1}{2}\mathbf{b} = \frac{1}{6}\mathbf{a} + \frac{1}{2}\mathbf{b}.
[2] (1 for subtraction setup, 1 for simplification)

14. AB=ba=(4162)=(34)\vec{AB} = \mathbf{b} - \mathbf{a} = \begin{pmatrix} 4-1 \\ 6-2 \end{pmatrix} = \begin{pmatrix} 3 \\ 4 \end{pmatrix}.
DC=cd=(9640)=(34)\vec{DC} = \mathbf{c} - \mathbf{d} = \begin{pmatrix} 9-6 \\ 4-0 \end{pmatrix} = \begin{pmatrix} 3 \\ 4 \end{pmatrix}.
Thus AB=DC\vec{AB} = \vec{DC}.
[2]

15. Type: Parallelogram. Reason: One pair of opposite sides (ABAB and DCDC) are equal and parallel.
Area: Using determinant of vectors AB=(34)\vec{AB} = \begin{pmatrix} 3 \\ 4 \end{pmatrix} and AD=da=(52)\vec{AD} = \mathbf{d} - \mathbf{a} = \begin{pmatrix} 5 \\ -2 \end{pmatrix}.
Area = det(AB,AD)=(3)(2)(4)(5)=620=26=26| \det(\vec{AB}, \vec{AD}) | = | (3)(-2) - (4)(5) | = | -6 - 20 | = |-26| = 26.
[5] (2 for type/reason, 3 for area calculation)

16. Point dividing ABAB in ratio m:nm:n (2:12:1) is na+mbm+n\frac{n\mathbf{a} + m\mathbf{b}}{m+n}.
c=1(25)+2(81)3=(25)+(162)3=(183)3=(61)\mathbf{c} = \frac{1\begin{pmatrix} 2 \\ 5 \end{pmatrix} + 2\begin{pmatrix} 8 \\ -1 \end{pmatrix}}{3} = \frac{\begin{pmatrix} 2 \\ 5 \end{pmatrix} + \begin{pmatrix} 16 \\ -2 \end{pmatrix}}{3} = \frac{\begin{pmatrix} 18 \\ 3 \end{pmatrix}}{3} = \begin{pmatrix} 6 \\ 1 \end{pmatrix}.
Coordinates of CC are (6,1)(6, 1).
[3] (1 for formula/setup, 1 for substitution, 1 for answer)

17. (a) A+B=(2+11+4023+0)=(3323)A+B = \begin{pmatrix} 2+1 & -1+4 \\ 0-2 & 3+0 \end{pmatrix} = \begin{pmatrix} 3 & 3 \\ -2 & 3 \end{pmatrix}.
(b) AB=(2103)(1420)=((2)(1)+(1)(2)(2)(4)+(1)(0)(0)(1)+(3)(2)(0)(4)+(3)(0))=(4860)AB = \begin{pmatrix} 2 & -1 \\ 0 & 3 \end{pmatrix} \begin{pmatrix} 1 & 4 \\ -2 & 0 \end{pmatrix} = \begin{pmatrix} (2)(1)+(-1)(-2) & (2)(4)+(-1)(0) \\ (0)(1)+(3)(-2) & (0)(4)+(3)(0) \end{pmatrix} = \begin{pmatrix} 4 & 8 \\ -6 & 0 \end{pmatrix}.
[3] (1 for sum, 2 for product)

18. 2A=(4206)2A = \begin{pmatrix} 4 & -2 \\ 0 & 6 \end{pmatrix}.
BT=(1240)B^T = \begin{pmatrix} 1 & -2 \\ 4 & 0 \end{pmatrix}.
2ABT=(412(2)0460)=(3046)2A - B^T = \begin{pmatrix} 4-1 & -2-(-2) \\ 0-4 & 6-0 \end{pmatrix} = \begin{pmatrix} 3 & 0 \\ -4 & 6 \end{pmatrix}.
[2]

19. (a) (3211)(xy)=(121)\begin{pmatrix} 3 & 2 \\ 1 & -1 \end{pmatrix} \begin{pmatrix} x \\ y \end{pmatrix} = \begin{pmatrix} 12 \\ -1 \end{pmatrix}.
(b) Det(M\mathbf{M}) = (3)(1)(2)(1)=5(3)(-1) - (2)(1) = -5.
M1=15(1213)\mathbf{M}^{-1} = \frac{1}{-5} \begin{pmatrix} -1 & -2 \\ -1 & 3 \end{pmatrix}.
(c) (xy)=15(1213)(121)\begin{pmatrix} x \\ y \end{pmatrix} = \frac{1}{-5} \begin{pmatrix} -1 & -2 \\ -1 & 3 \end{pmatrix} \begin{pmatrix} 12 \\ -1 \end{pmatrix}.
x=15(12+2)=2x = \frac{1}{-5} (-12 + 2) = 2.
y=15(123)=3y = \frac{1}{-5} (-12 - 3) = 3.
[5] (1 for matrix form, 2 for inverse, 2 for solution)

20. (a) Rotation 9090^\circ anti-clockwise about the origin (0,0)(0,0).
(b) (0110)(34)=(43)\begin{pmatrix} 0 & -1 \\ 1 & 0 \end{pmatrix} \begin{pmatrix} 3 \\ 4 \end{pmatrix} = \begin{pmatrix} -4 \\ 3 \end{pmatrix}.
Image is (4,3)(-4, 3).
[3] (2 for description, 1 for image)