Topic – E1.15
Tara goes on a journey by train.
The train leaves at 06 48.
The journey takes 12 hours and 35 minutes.
Find the time when Tara arrives.
▶️ Answer/Explanation
Ans: 19:23 or 7:23 pm
Start time: 06:48
Add 12 hours: 18:48
Add 35 minutes: 19:23
Topic – E1.3
From the list, write down:
(a) a cube number
(b) a prime number.
▶️ Answer/Explanation
Ans:
(a) 64 (since 4×4×4 = 64)
(b) 61 (only number divisible by 1 and itself)
Topic – E9.3
The stem-and-leaf diagram shows the heights, in centimetres, of some plants:
(a) Find the median height.
(b) Work out the mean height.
▶️ Answer/Explanation
Ans:
(a) 12.2 cm (7th value in ordered list of 13 values)
(b) 12.1 cm (sum of all heights ÷ 13 = 157.3 ÷ 13)
Topic – E1.13
Shubhu invests \($750\) in a savings account for 5 years. The account pays simple interest at a rate of 1.8% per year.
Calculate the total interest she earns during the 5 years.
▶️ Answer/Explanation
Ans: \$67.50
Simple Interest = Principal × Rate × Time
= \$750 × 0.018 × 5
= \$67.50
Topic – E4.1
The diagram shows triangle ABC.
M is the midpoint of AC.
Triangle ABC is rotated 180° about centre M.
The image and the original triangle together form a quadrilateral ABCD.
(a) Write down the mathematical name of the quadrilateral ABCD.
(b) Find angle BAD.
▶️ Answer/Explanation
Ans:
(a) Parallelogram (opposite sides equal and parallel)
(b) 68° (180° – 112° from rotation properties)
Topic – E8.1
Rama asks a group of students how they travel to school.
The table shows the probability of how a student, chosen at random, travels to school.
(a) Complete the table.
(b) There are 1800 students at the school. Find the expected number of students that walk to school.
▶️ Answer/Explanation
Ans:
(a) Other = 1 – (0.4 + 0.32 + 0.17) = 0.11
(b) Expected number = 1800 × 0.32 = 576 students
For part (a), probabilities must sum to 1. For part (b), multiply total students by walk probability.
Topic – E1.4
Without using a calculator, work out $1\frac{5}{6} \div \frac{11}{15}$.
You must show all your working and give your answer as a mixed number in its simplest form.
▶️ Answer/Explanation
Ans: $2\frac{1}{2}$
First convert mixed number: $1\frac{5}{6} = \frac{11}{6}$
Division becomes multiplication by reciprocal: $\frac{11}{6} \times \frac{15}{11} = \frac{165}{66}$
Simplify: $\frac{165}{66} = \frac{5}{2} = 2\frac{1}{2}$
The 11’s cancel out, then divide numerator and denominator by 33.
Topic – E1.1
Find the highest common factor (HCF) of 48 and 80.
▶️ Answer/Explanation
Ans: 16
Prime factors of 48: $2^4 \times 3$
Prime factors of 80: $2^4 \times 5$
Common factors: $2^4 = 16$
Therefore, HCF is 16.
Topic – E2.2
$P = \frac{2w y^2}{3}$
Find the positive value of $y$ when $P = 108$ and $w = 8$.
▶️ Answer/Explanation
Ans: 4.5 or $\frac{9}{2}$
$108 = \frac{2 \times 8 \times y^2}{3}$
$108 = \frac{16y^2}{3}$
$324 = 16y^2$
$y^2 = 20.25$ → $y = 4.5$ (positive value)
Topic – E7.1
$\overrightarrow{AB} = \begin{pmatrix} 7 \\ -3 \end{pmatrix}$
(a) Find $3\overrightarrow{AB}$.
(b) Find $|\overrightarrow{AB}|$.
▶️ Answer/Explanation
Ans:
(a) $3\begin{pmatrix} 7 \\ -3 \end{pmatrix} = \begin{pmatrix} 21 \\ -9 \end{pmatrix}$
(b) $|\overrightarrow{AB}| = \sqrt{7^2 + (-3)^2} = \sqrt{49 + 9} = \sqrt{58} ≈ 7.62$
For (a), multiply each component by 3. For (b), use Pythagoras’ theorem.
Topic – E5.4
A bronze sphere has radius 3.6 cm.
The density of bronze is 8.05 g/cm3.
Find the mass of the sphere.
Give your answer in kilograms, correct to the nearest gram.
[The volume, V, of a sphere with radius r is V = $\frac{4}{3}\pi r^3$.]
[Density = mass ÷ volume.]
▶️ Answer/Explanation
Ans: 1.573 kg
1. Calculate volume: $\frac{4}{3}\pi(3.6)^3 ≈ 195.432 cm^3$
2. Find mass: 195.432 × 8.05 ≈ 1573.23 g
3. Convert to kg: 1573.23 g = 1.57323 kg
4. Round to nearest gram: 1.573 kg
Topic – E1.13
Oliver sent 22% more messages in June than in May.
He sent 305 messages in June.
Find how many more messages he sent in June than in May.
▶️ Answer/Explanation
Ans: 55
1. Let May messages = M
2. June messages = 1.22 × M = 305
3. Solve for M: M = 305 ÷ 1.22 = 250
4. Difference: 305 – 250 = 55 more messages
Topic – E2.6
The graph of y = 2x + 1 is drawn on the grid.
By shading the unwanted regions of the grid, find and label the region R which satisfies these inequalities:
y ≥ 2x + 1 y ≥ 1 4x + 3y < 12
▶️ Answer/Explanation
Ans:
1. Draw y=2x+1 as solid line, shade above it
2. Draw y=1 as solid line, shade above it
3. Draw 4x+3y=12 as dashed line, shade below it
4. The region satisfying all three is the triangular area where all shadings overlap
Topic – E9.4
The box-and-whisker plot shows information about the mass, in kg, of some parcels.
(a) Find the mass of the heaviest parcel.
(b) Find the interquartile range.
▶️ Answer/Explanation
Ans: (a) 3.3 kg (b) 0.55 kg
(a) The rightmost point on the plot shows the maximum mass = 3.3 kg
(b) IQR = Q3 – Q1 = 2.75 – 2.2 = 0.55 kg (read from the box ends)
Topic – E2.2
T = $\sqrt{3d – e}$
Rearrange the formula to make d the subject.
▶️ Answer/Explanation
Ans: d = $\frac{T^2 + e}{3}$
1. Square both sides: T² = 3d – e
2. Add e to both sides: T² + e = 3d
3. Divide by 3: d = (T² + e)/3
Topic – E5.4
A cylinder with height 12.5 cm has a curved surface area of 105π cm².
Calculate the volume of the cylinder.
▶️ Answer/Explanation
Ans: 693 or 692.7 to 692.8 cm³
1. Find radius using curved surface area formula: 2πrh = 105π → r = 105/(2×12.5) = 4.2 cm
2. Volume formula: πr²h = π×(4.2)²×12.5
3. Calculate: π×17.64×12.5 ≈ 693 cm³
Topic – E2.4
(a) Simplify $(64y^{27})^{\frac{2}{3}}$
(b) Simplify $\frac{x – 5}{x^2 – 25}$
▶️ Answer/Explanation
Ans:
(a) $16y^{18}$
1. Cube root first: $(64y^{27})^{1/3} = 4y^9$
2. Then square: $(4y^9)^2 = 16y^{18}$
(b) $\frac{1}{x+5}$
1. Factor denominator: $x^2-25 = (x+5)(x-5)$
2. Cancel (x-5) terms
Topic – E1.11
$F$ is proportional to the product of $m$ and $a$.
Calculate the percentage change in $F$ when $m$ is increased by 40% and $a$ is decreased by 15%.
▶️ Answer/Explanation
Ans: 19%
1. New m = 1.4m (40% increase)
2. New a = 0.85a (15% decrease)
3. New F = k×(1.4m)×(0.85a) = 1.19kma
4. Percentage change = (1.19 – 1)×100 = 19%
Topic – E6.2
Calculate the obtuse angle $PRQ$.
▶️ Answer/Explanation
Ans: 116.9°
1. Use sine rule: $\frac{QR}{\sin P} = \frac{PQ}{\sin R}$
2. $\sin R = \frac{PQ \sin P}{QR} = \frac{13.5 \sin 42°}{18}$ ≈ 0.5
3. Acute angle would be ≈63.1°
4. Obtuse angle = 180° – 63.1° = 116.9°
Topic – E2.2
$(x+a)(x+2)(2x+3)$ is equivalent to $2x^3+bx^2+cx-18$.
Find the value of each of $a$, $b$ and $c$.
▶️ Answer/Explanation
Ans: a = -3, b = 1, c = -15
1. Constant term: a×2×3 = -18 → a = -3
2. Expand first two brackets: (x² – x – 6)(2x + 3)
3. Final expansion: 2x³ + x² – 15x – 18
4. Compare coefficients: b=1, c=-15
Topic – E6.1
The diagram shows a cuboid ABCDEFGH.
AB = 14 cm, BC = 5 cm and CG = 8 cm.
M is the midpoint of HG.
(a) Calculate BM.
(b) Calculate the angle that BM makes with the base ABCD.
▶️ Answer/Explanation
(a) Ans: 11.7 cm
First find horizontal distance from B to M: 7 cm (half AB) and 5 cm (BC).
Then use 3D Pythagoras: √(7² + 5² + 8²) = √(49 + 25 + 64) = √138 ≈ 11.7 cm
(b) Ans: 43.0°
Angle is between BM and its projection on base. Vertical component is 8 cm.
tanθ = 8/√(7² + 5²) → θ = tan⁻¹(8/√74) ≈ 43.0°
Topic – E2.5
Find the coordinates of the point where the line 4x + y = 9 intersects the curve y + x² = 5.
▶️ Answer/Explanation
Ans: (2, 1)
From line equation: y = 9 – 4x
Substitute into curve: (9 – 4x) + x² = 5 → x² – 4x + 4 = 0
Solve: (x – 2)² = 0 → x = 2
Find y: y = 9 – 4(2) = 1