Topic – C4.6
Write down the mathematical name for this type of angle.
▶️ Answer/Explanation
Ans: Obtuse
An angle between 90° and 180° is called an obtuse angle. Since the given angle falls in this range, its mathematical name is “obtuse”.
Topic – C1.1
Write down the value of the 8 in the number 58 317.
▶️ Answer/Explanation
Ans: 8000
In the number 58,317, the digit 8 is in the thousands place. Therefore, its value is 8 × 1000 = 8000.
Topic – C2.5
Complete these statements.
(a) When \( x = \ldots, x + 3 = 8 \).
(b) When \( 7y = 63, 10y = \ldots \).
▶️ Answer/Explanation
Ans: (a) 5 (b) 90
(a) Subtract 3 from both sides: \( x = 8 – 3 = 5 \).
(b) First solve for y: \( y = 63 ÷ 7 = 9 \). Then multiply by 10: \( 10y = 10 × 9 = 90 \).
Topic – C1.3
Find the value of \( \sqrt[3]{5832} \).
▶️ Answer/Explanation
Ans: 18
We need to find a number that when multiplied by itself three times equals 5832. Testing 18: \( 18 × 18 × 18 = 5832 \), so the cube root is 18.
Topic – C1.13
A watch costs $12,400.
In a sale there is a discount of 16%.
Calculate the amount of the discount.
▶️ Answer/Explanation
Ans: $1984
Calculate 16% of \($12,400\): \( 0.16 × 12400 = 1984 \). The discount amount is \($1984\).
Topic – C9.3
(a) Mei writes down five integers:
- The lowest integer is 8
- The range is 9
- The median is 15
- The total of the five integers is 66
- There is no mode
Write down the five integers.
(b) Huan writes down four numbers.
The mean of these four numbers is 17.
He writes down a fifth number.
The mean of these five numbers is 20.
Find the fifth number.
▶️ Answer/Explanation
Ans: (a) 8, 10, 15, 16, 17 (b) 32
(a) Range = 9 ⇒ highest = 8+9 = 17. Median is 15 (third number). Total 66 ⇒ middle numbers sum to 66-8-17=41. No mode ⇒ all numbers distinct.
(b) Original total = 4×17 = 68. New total = 5×20 = 100. Fifth number = 100-68 = 32.
Topic – C1.15
Arjun lives in Delhi and Haru lives in Tokyo.
They play a computer game online at the same time.
They start at 14 45 Tokyo local time.
The game lasts 3 hours 50 minutes.
The local time in Delhi is 3 hours 30 minutes behind the local time in Tokyo.
Find the local time in Delhi when the game finishes.
▶️ Answer/Explanation
Ans: 15:05 or 3:05 pm
Tokyo finish time: 14:45 + 3h50m = 18:35. Delhi is 3h30m behind ⇒ 18:35 – 3h30m = 15:05.
Topic – C4.6
The diagram shows an isosceles triangle.
Find the value of x.
▶️ Answer/Explanation
Ans: 98
In an isosceles triangle, two angles are equal (41° each). Total angles = 180° ⇒ x = 180 – 41 – 41 = 98°.
Topic – C9.4
The stem-and-leaf diagram shows the time, in minutes, it takes each of 15 people to complete a race.
Find:
(a) the mode
(b) the range
(c) the median
▶️ Answer/Explanation
Ans: (a) 27 (b) 15 (c) 25
(a) Mode = most frequent = 27 (appears 3 times)
(b) Range = 31 – 16 = 15 minutes
(c) Median (8th value) = 25 minutes
Topic – C4.6
AB and CD are parallel lines.
Find the value of x.
▶️ Answer/Explanation
Ans: 83
Using parallel line properties: x + 52° = 135° ⇒ x = 135° – 52° = 83°.
Topic – C1.9
Write 0.03682 correct to 2 significant figures.
▶️ Answer/Explanation
Ans: 0.037
The third digit (6) after the first two significant figures (3 and 6) is 5 or greater, so we round up the second significant figure from 6 to 7.
Topic – C1.16
The table shows some information about Amir’s shopping.
Fruit | Cost per kilogram | Number of kilograms Amir buys | Cost |
---|---|---|---|
Oranges | $2.35 | 3.2 | $…… |
Bananas | $…… | 2.8 | $…… |
Total | $13.54 |
Complete the table.
▶️ Answer/Explanation
Ans:
Oranges cost: 3.2 × $2.35 = $7.52
Bananas cost: $13.54 – $7.52 = $6.02
Bananas cost per kg: $6.02 ÷ 2.8 = $2.15
Topic – C9.5
For each of 10 people working in an office, the scatter diagram shows their salary and the value of their car.
(a) One of these people has a salary of $28,000. Find the value of their car.
(b) Another person starts to work in the office. Their salary is $54,000 and the value of their car is $6,100. Plot this information on the scatter diagram.
(c) What type of correlation is shown in the scatter diagram?
▶️ Answer/Explanation
Ans:
(a) $4,800 (estimated from the scatter plot)
(b) Point should be plotted at (54,000, 6,100)
(c) Positive correlation (as salary increases, car value tends to increase)
Topic – C2.2
Factorise completely.
42mk – 35m
▶️ Answer/Explanation
Ans: 7m(6k – 5)
First find the common factor of both terms: 7m
Divide each term by 7m: 42mk ÷ 7m = 6k, -35m ÷ 7m = -5
Write as product: 7m × (6k – 5)
Topic – C1.1
Find the highest common factor (HCF) of 140 and 126.
▶️ Answer/Explanation
Ans: 14
Prime factors of 140: 2 × 2 × 5 × 7
Prime factors of 126: 2 × 3 × 3 × 7
Common factors are 2 and 7
HCF = 2 × 7 = 14
Topic – C2.4
Simplify.
(a) \( n^5 \times n \)
(b) \( 8x^6 \div 2x^2 \)
▶️ Answer/Explanation
(a) Ans: \( n^6 \)
When multiplying with the same base, add the exponents: \( n^5 \times n^1 = n^{5+1} = n^6 \)
(b) Ans: \( 4x^4 \)
Divide coefficients (8÷2=4) and subtract exponents (6-2=4): \( 4x^{6-2} = 4x^4 \)
Topic – C5.3
The circumference of a circle is 59 cm. Calculate the radius of the circle.
▶️ Answer/Explanation
Ans: 9.39 cm
Using circumference formula \( C = 2\pi r \)
Rearrange to find radius: \( r = \frac{C}{2\pi} = \frac{59}{2 \times 3.142} \)
Calculate: \( \frac{59}{6.284} ≈ 9.39 \) cm
Topic – C1.9
By writing each number in the calculation correct to 1 significant figure, find an estimate for the value of:
\( \frac{36.9 + 24.2}{3.8 – 1.2} \)
▶️ Answer/Explanation
Ans: 20
Round numbers: 36.9→40, 24.2→20, 3.8→4, 1.2→1
Numerator: 40 + 20 = 60
Denominator: 4 – 1 = 3
Estimate: \( \frac{60}{3} = 20 \)
Topic – C1.13
Indira invests $6000 at a rate of r% per year simple interest.
At the end of 4 years the value of her investment is $6840.
Find the value of r.
▶️ Answer/Explanation
Ans: 3.5
Interest earned = $6840 – $6000 = $840
Simple interest formula: \( I = \frac{P \times r \times t}{100} \)
Substitute values: \( 840 = \frac{6000 \times r \times 4}{100} \)
Solve for r: \( r = \frac{840 \times 100}{6000 \times 4} = 3.5 \)%
Topic – C5.2
Find the area of this trapezium.
▶️ Answer/Explanation
Ans: 66 cm²
Trapezium area formula: \( \frac{1}{2} \times (a + b) \times h \)
Substitute values: \( \frac{1}{2} \times (8 + 14) \times 6 \)
Calculate: \( \frac{1}{2} \times 22 \times 6 = 66 \) cm²
Topic – C1.8
(a) Write these numbers in standard form.
(i) 45 000
(ii) 0.0063
(b) Calculate 8.2 × 10-1 × 150000. Give your answer in standard form.
▶️ Answer/Explanation
Ans:
(a)(i) 4.5 × 104
(a)(ii) 6.3 × 10-3
(b) 1.23 × 105
For (a), move decimal point to get a number between 1-10 and count places moved.
For (b), multiply 8.2 × 150000 = 1,230,000, then adjust to standard form.
Topic – C1.10
The length, s metres, of a ship is 287 m, correct to the nearest metre.
Complete this statement about the value of s.
…… ≤ s < ……
▶️ Answer/Explanation
Ans: 286.5 ≤ s < 287.5
When rounding to nearest metre, any value from 286.5 up to but not including 287.5 would round to 287.
The lower bound is 287 – 0.5 = 286.5
The upper bound is 287 + 0.5 = 287.5
Topic – C8.1
The table shows the number of people in a town who are left-handed and the number who are right-handed.
Left-handed | Right-handed | Total | |
---|---|---|---|
Number of people | 8 400 | 48 600 | 57 000 |
Write down the probability that a person, chosen at random, is left-handed.
▶️ Answer/Explanation
Ans: 8400/57000 or equivalent simplified fraction
Probability = Number of left-handed people / Total number of people
8400 ÷ 57000 = 0.147 (3sf) or 14/95 when simplified
This represents about 14.7% chance.
Topic – C5.1
(a) Change 1.2 m2 into mm2.
(b) The speed limit on a road is 80 km/h.
Sophie drives at a speed of 1200 m/min.
Show that Sophie drives at a speed lower than the speed limit.
▶️ Answer/Explanation
Ans:
(a) 1,200,000 mm2
(b) Sophie’s speed is 72 km/h which is less than 80 km/h
For (a): 1 m = 1000 mm, so 1 m2 = 1,000,000 mm2. 1.2 × 1,000,000 = 1,200,000
For (b): 1200 m/min × 60 = 72,000 m/h = 72 km/h. Since 72 < 80, she’s under limit.
Topic – C5.3
Calculate the area of a semicircle with radius 10 cm.
▶️ Answer/Explanation
Ans: 157 cm2 (to 3sf)
Area of full circle = π × r2 = π × 102 = 100π
Area of semicircle = ½ × 100π = 50π
Using π ≈ 3.142: 50 × 3.142 ≈ 157.1 cm2
Rounded to 3 significant figures: 157 cm2