Topic – E1.4
Write 24.07839
(a) correct to 2 decimal places
(b) correct to the nearest 10.
▶️ Answer/Explanation
(a) 24.08
Look at the third decimal (8) which rounds up the second decimal (7) to 8.
(b) 20
The digit in the tens place is 2, and the next digit (4) is less than 5, so we round down to 20.
Topic – E1.6
Write down the number that is 9 greater than −23.
▶️ Answer/Explanation
-14
Simply add 9 to -23: -23 + 9 = -14.
Topic – E2.5
$v = u + at$
Find the value of $v$ when $u = 30$, $a = -2$ and $t = 7$.
▶️ Answer/Explanation
16
Substitute the values into the formula: $v = 30 + (-2) \times 7$
Calculate: $30 – 14 = 16$
Topic – E5.1
Change 62 000 millimetres into kilometres.
▶️ Answer/Explanation
0.062 km
First convert mm to m: 62000 mm ÷ 1000 = 62 m
Then convert m to km: 62 m ÷ 1000 = 0.062 km
Topic – E4.6
The diagram shows two intersecting straight lines crossing two parallel lines.
Find the value of $x$.
▶️ Answer/Explanation
64
Using the property of parallel lines, the angle adjacent to x is equal to 50°.
Then, x + 50° = 114° (straight line), so x = 114° – 50° = 64°.
Topic – E1.1
(a) Explain why 111 is not a prime number.
(b) Find a prime number between 110 and 120.
▶️ Answer/Explanation
(a) Ans: 111 is divisible by 3 (1+1+1=3) and 37 (3×37=111)
(b) Ans: 113
Checking numbers between 110-120: 111 (divisible by 3), 113 (prime), 117 (divisible by 3), 119 (7×17).
Topic – E4.6
Find the bearing of Q from P.
▶️ Answer/Explanation
Ans: 231°
Bearings are measured clockwise from North.
180° (South) + (90° – 39°) = 180° + 51° = 231°
Topic – E1.4
Without using a calculator, work out $3\frac{1}{8} – 1\frac{3}{4}$.
You must show all your working and give your answer as a mixed number in its simplest form.
▶️ Answer/Explanation
Ans: $1\frac{3}{8}$
Convert to improper fractions: $\frac{25}{8} – \frac{7}{4}$
Common denominator (8): $\frac{25}{8} – \frac{14}{8} = \frac{11}{8}$
Convert to mixed number: $1\frac{3}{8}$
Topic – E1.1
Write 90 as a product of its prime factors.
▶️ Answer/Explanation
Ans: $2 \times 3^2 \times 5$
Break down 90: 90 = 2 × 45
45 = 3 × 15
15 = 3 × 5
Final form: 2 × 3 × 3 × 5 or $2 \times 3^2 \times 5$
Topic – E2.2
Expand and simplify: $2(t + w) + 3(w – t)$
▶️ Answer/Explanation
Ans: $5w – t$
First expand: $2t + 2w + 3w – 3t$
Combine like terms: $(2t – 3t) + (2w + 3w)$
Simplify: $-t + 5w$ or $5w – t$
Topic – E4.4
The two shapes are mathematically similar.
(a) Find the value of h.
(b) The area of the smaller shape is 16 cm². Calculate the area of the larger shape.
▶️ Answer/Explanation
(a) Ans: 3.5
Using similarity ratio: $\frac{9}{5} = \frac{6.3}{h}$
$h = \frac{6.3 \times 5}{9} = 3.5$ cm
(b) Ans: 51.84
Area ratio is square of length ratio: $(\frac{9}{5})^2 = \frac{81}{25}$
Larger area = $16 \times \frac{81}{25} = 51.84$ cm²
Topic – E2.9
The diagram shows a speed-time graph for 16 seconds of a car journey.
(a) Find the deceleration of the car in the final 4 seconds.
(b) Find the total distance travelled during the 16 seconds.
▶️ Answer/Explanation
(a) Ans: 2.5 m/s²
Deceleration = $\frac{10}{4} = 2.5$ m/s²
(b) Ans: 140 m
Distance = area under graph = rectangle + triangle
$(10 \times 12) + (\frac{1}{2} \times 4 \times 10) = 120 + 20 = 140$ m
Topic – E1.7
(a) $3^{3p} \times 3^{2p} = 729$
Find the value of p.
(b) Simplify $(32x^{10})^{\frac{1}{5}}$
▶️ Answer/Explanation
(a) Ans: 1.2
$3^{5p} = 3^6$ (since $729 = 3^6$)
$5p = 6 \Rightarrow p = \frac{6}{5} = 1.2$
(b) Ans: $2x^2$
$(32)^{\frac{1}{5}} = 2$ and $(x^{10})^{\frac{1}{5}} = x^2$
Final answer: $2x^2$
Topic – E2.2
$y = 2w^2 – x$
Rearrange the formula to make w the subject.
▶️ Answer/Explanation
Ans: $w = \pm\sqrt{\frac{y + x}{2}}$
Start: $y = 2w^2 – x$
Add x to both sides: $y + x = 2w^2$
Divide by 2: $\frac{y + x}{2} = w^2$
Square root both sides: $w = \pm\sqrt{\frac{y + x}{2}}$
Topic – E1.2
(a) On the Venn diagram, shade the region P ∪ Q′.
(b) n(ξ) = 20, n(A ∪ B)′ = 1, n(A) = 12, n(B) = 10
Complete the Venn diagram.
▶️ Answer/Explanation
(a) Ans:
P ∪ Q′ means all elements in P or not in Q.
(b) Ans:
n(A ∩ B) = n(A) + n(B) – n(A ∪ B) = 12 + 10 – 19 = 3
A only = 12 – 3 = 9, B only = 10 – 3 = 7, outside = 1
Topic – E1.3
Find the lowest common multiple (LCM) of \( 12x^8 \) and \( 8x^{12} \).
▶️ Answer/Explanation
Ans: \( 24x^{12} \)
1. Find LCM of coefficients: LCM of 12 and 8 is 24
2. For variables, take highest power: \( x^{12} \)
3. Combine them: \( 24x^{12} \)
Topic – E4.7
(a)
A, B and C are points on a circle, centre O.
Angle \( OBA = 28^\circ \).
Find angle \( ACB \).
(b)
P, Q and R are points on a circle.
TU is a tangent to the circle at P.
Angle \( TPR = 47^\circ \) and angle \( PRQ = 52^\circ \).
Find angle \( RPQ \).
▶️ Answer/Explanation
Ans: (a) 62° (b) 81°
(a) Triangle OAB is isosceles (OA=OB=radius). Angle AOB = 180° – 2×28° = 124°. Angle ACB is half of angle AOB = 62°.
(b) Angle QPU = angle PRQ = 52° (alternate segment theorem). Angle RPQ = 180° – 47° – 52° = 81°.
Topic – E5.4
A solid cylinder has radius 5 cm and height 8 cm.
Calculate the total surface area of the cylinder.
▶️ Answer/Explanation
Ans: 408 cm² (or 408.4 to 408.5)
1. Curved surface area: \( 2πrh = 2×π×5×8 = 80π \)
2. Two circular ends: \( 2×πr² = 2×π×25 = 50π \)
3. Total surface area: \( 80π + 50π = 130π ≈ 408.4 \) cm²
Topic – E2.7
Find the nth term of each sequence.
(a) 11, 8, 5, 2, -1, …
(b) 1, 5, 25, 125, 625, …
▶️ Answer/Explanation
Ans: (a) \( 14 – 3n \) (b) \( 5^{n-1} \)
(a) This is an arithmetic sequence. First term (a)=11, common difference (d)=-3. nth term = a + (n-1)d = 11 + (n-1)(-3) = 14 – 3n.
(b) This is a geometric sequence where each term is multiplied by 5. First term=1, common ratio=5. nth term = \( 5^{n-1} \).
Topic – E1.10
The area of a rectangle is 55.2 cm², correct to 1 decimal place.
The length of the rectangle is 9 cm, correct to the nearest cm.
Calculate the upper bound of the width of the rectangle.
▶️ Answer/Explanation
Ans: 6.5 cm
1. Upper bound of area: 55.25 cm²
2. Lower bound of length: 8.5 cm
3. Upper bound of width = upper bound area / lower bound length
4. Calculation: 55.25 ÷ 8.5 = 6.5 cm
Topic – E2.10
The line $y = x + 1$ intersects the curve $y = x^2 + x – 3$ at two points.
Find the coordinates of the two points.
▶️ Answer/Explanation
Ans: (2, 3) and (-2, -1)
Set equations equal: $x + 1 = x^2 + x – 3$
Simplify to $x^2 – 4 = 0$
Solve: $x = 2$ or $x = -2$
Find y-values: When $x=2$, $y=3$; when $x=-2$, $y=-1$
Topic – E1.11
$x$ is inversely proportional to the square root of $w$. When $w = 16$, $x = 3$.
Find $x$ in terms of $w$.
▶️ Answer/Explanation
Ans: $x = \frac{12}{\sqrt{w}}$
General form: $x = \frac{k}{\sqrt{w}}$
Substitute given values: $3 = \frac{k}{\sqrt{16}}$ → $3 = \frac{k}{4}$
Solve for k: $k = 12$
Final equation: $x = \frac{12}{\sqrt{w}}$
Topic – E9.4
Some students record their reaction times.
The table shows the results.
Reaction time (t seconds) | $0 < t \leq 6$ | $6 < t \leq 10$ |
---|---|---|
Frequency | 18 | 16 |
On a histogram, the height of the block for the $0 < t \leq 6$ interval is 7.5 cm.
Calculate the height of the block for the $6 < t \leq 10$ interval.
▶️ Answer/Explanation
Ans: 10 cm
Find frequency density for first interval: $18 \div 6 = 3$ per second
Height corresponds to frequency density: $7.5 \text{cm} = 3$ per second
Find frequency density for second interval: $16 \div 4 = 4$ per second
Calculate height: $(4/3) \times 7.5 = 10$ cm
Topic – E2.2
Simplify.
$\frac{ax – 2a – x + 2}{a^2 – 1}$
▶️ Answer/Explanation
Ans: $\frac{x – 2}{a + 1}$
Factor numerator: $a(x – 2) – (x – 2) = (x – 2)(a – 1)$
Factor denominator: $a^2 – 1 = (a – 1)(a + 1)$
Cancel common factor $(a – 1)$
Final simplified form: $\frac{x – 2}{a + 1}$
Topic – E2.4
The derivative of $2ax^7 + 3x^k$ is $42x^6 + 15x^{k-1}$.
Find the value of $a$ and the value of $k$.
▶️ Answer/Explanation
Ans: $a = 3$, $k = 5$
Find derivative: $\frac{d}{dx}(2ax^7 + 3x^k) = 14ax^6 + 3kx^{k-1}$
Set equal to given derivative: $14a = 42$ and $3k = 15$
Solve for a: $a = 42/14 = 3$
Solve for k: $k = 15/3 = 5$
Topic – E7.1
The diagram shows a parallelogram $OPQT$.
The position vector of $P$ is $\mathbf{a}$ and the position vector of $T$ is $\mathbf{b}$.
$K$ is on $PQ$ so that $PK : KQ = 3 : 1$.
The lines $OK$ and $TQ$ are extended to meet at $X$.
Find the position vector of $X$ in terms of $\mathbf{a}$ and $\mathbf{b}$.
Give your answer in its simplest form.
▶️ Answer/Explanation
Ans: $\mathbf{b} + \frac{4}{3}\mathbf{a}$
Find vector $\overrightarrow{OK} = \mathbf{a} + \frac{3}{4}\mathbf{b}$ (since PK:KQ=3:1)
Find vector equation of line OX: $\lambda(\mathbf{a} + \frac{3}{4}\mathbf{b})$
Find vector equation of line TX: $\mathbf{b} + \mu(\mathbf{a})$
Solve for intersection point to get $\lambda = \frac{4}{3}$
Final position vector: $\mathbf{b} + \frac{4}{3}\mathbf{a}$