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Cambridge Lower Secondary Maths: Stage 8

Stage 8 of the Cambridge Lower Secondary Mathematics (0862) curriculum framework, usually Year 8 (ages 12 to 13). Here is what each part asks, a practice question for each, and the mistakes that cost the most marks.

Practise Stage 8 as a game

The 58 parts of Stage 8

Each part with one practice question, made by the same engine your child plays.

Integers, powers and roots

The order of brackets, indices (square and cube roots) and operations

Work out
7 × (3 + 2)

  1. 42
  2. 23
  3. 35
  4. 12
Show the answer

35. Brackets first: 3 + 2 = 5, then 7 × 5 = 35.

Multiply and divide integers

−30 ÷ (−6) = ?

  1. −5
  2. 5
  3. −36
  4. 11
Show the answer

5. 30 ÷ 6 = 5. The signs are the same, so the answer is positive. 5.

Factors, multiples, prime factors, HCF and LCM

Write 12 as a product of prime factors.

  1. 2² × 3
  2. 2² × 3²
  3. 2³ × 3
  4. 4 × 3
Show the answer

2² × 3. Keep dividing by primes: 12 = 2² × 3.

Natural numbers, integers and rational numbers

Which of these is a natural number?

  1. −3
  2. 1/2
  3. 2.5
  4. 1
Show the answer

1. Natural numbers are 1, 2, 3, … ; integers add 0 and the negatives; rational numbers are any fraction of integers, so they add decimals like 2.5 and fractions like 1/2.

Positive and zero indices; index laws for multiplying and dividing

Simplify x⁹ × x³

  1. x²⁷
  2. 2x¹²
  3. x⁶
  4. x¹²
Show the answer

x¹². Multiplying: add the powers. 9 + 3 = 12.

Squares of negative and positive numbers, and the matching square roots

Which numbers, squared, give 9?

  1. −3 only
  2. 3 only
  3. 9 and −9
  4. 3 and −3
Show the answer

3 and −3. 3² = 9 and (−3)² = 9 too. Every positive number has two square roots.

Positive and negative cube numbers, and the matching cube roots

What is ∛(−216)?

  1. −72
  2. 6
  3. −6
  4. −7
Show the answer

−6. (−6) × (−6) × (−6) = −216: three negatives multiply to a negative. So ∛(−216) = −6. (A square root of a negative has no real answer, but a cube root does.)

Place value, ordering and rounding

Multiply and divide by 0.1 and 0.01

6 ÷ 0.01 = ?

  1. 6000
  2. 0.06
  3. 60
  4. 600
Show the answer

600. Dividing by 0.01 makes a number BIGGER: it is the same as multiplying by 100. 600.

Round to a given number of significant figures

Round 0.02276 to 3 significant figures.

  1. 0.0231
  2. 0.0227
  3. 0.0230
  4. 0.0228
Show the answer

0.0228. The zeros at the front only hold the place: they are not significant. Count 3 digits from the first non-zero one: 0.0228.

Fractions, decimals, percentages, ratio and proportion

Fractions that equal recurring decimals

Which fraction is equal to a RECURRING decimal?

  1. 7/20
  2. 5/12
  3. 1/4
  4. 1/5
Show the answer

5/12. 5/12 = 0.4167…, and the digits go on repeating. The others stop.

Subtract mixed numbers; answer as a mixed number in simplest form

5 5/6 − 3 1/6 = ?
(simplest form)

  1. 2 2/3
  2. 8 2/3
  3. 2 5/6
  4. 1 2/3
Show the answer

2 2/3. Wholes: 5 − 3 = 2. Fractions: 5/6 − 1/6 = 2/3. Together 2 2/3.

Multiply an integer by a mixed number; divide an integer by a proper fraction

1/6 ÷ 1/7 = ?

  1. 1/42
  2. 2/13
  3. 6/7
  4. 7/6
Show the answer

7/6. Flip the second fraction and multiply: 1/6 × 7/1 = 7/6.

Simplify calculations with decimals or fractions, including brackets

Which is the same as 7 × (24 + 4)?

  1. 7 × 24 × 4
  2. 7 + 24 × 4
  3. 7 × 24 + 7 × 4
  4. 7 × 24 + 4
Show the answer

7 × 24 + 7 × 4. Multiplying a bracket multiplies EVERYTHING inside it: 7 × 24 + 7 × 4 = 168 + 28 = 196.

Percentage increase and decrease; absolute change

Decrease $60 by 10%.

  1. $6
  2. $66
  3. $54
  4. $50
Show the answer

$54. 10% of 60 is 6. 60 − 6 = 54.

Compare and order positive and negative decimals and fractions

Which is the SMALLEST?
⅖ 0.3 −1.2 −0.5

  1. −0.5
  2. 0.3
  3. −1.2
  4. ⅖
Show the answer

−1.2. As decimals: ⅖ = 0.4, 0.3 = 0.3, −1.2 = −1.2, −0.5 = −0.5. On a number line the smallest is the one furthest left: −1.2. Below zero, a bigger number AFTER the minus sign is SMALLER.

Multiply decimals by integers and by decimals

0.9 × 0.3 = ?

  1. 2.7
  2. 0.27
  3. 1.2
  4. 0.027
Show the answer

0.27. Multiply as whole numbers: 9 × 3 = 27. Count the decimal places in the question (1 + 1) and put that many back: 0.27.

Divide decimals by numbers with one decimal place

0.9 ÷ 0.3 = ?

  1. 30
  2. 3
  3. 0.3
  4. 2.8
Show the answer

3. Multiply both numbers by 10 so the divisor is whole: 9 ÷ 3 = 3. The answer is bigger than the number you started with, because you are dividing by less than 1.

How ratio and direct proportion relate

Boys and girls in a club are in the ratio 4:3.
What PROPORTION of the club are boys?

  1. 4%
  2. 4/7
  3. 4/3
  4. 3/7
Show the answer

4/7. 4:3 means 4 boys in every 7 children, so the proportion of boys is 4/7.

Simplify and compare ratios in different units

Write the ratio 15 minutes : 2 hours in its simplest form.

  1. 15 : 2
  2. 8 : 1
  3. 1 : 8
  4. 1 : 80
Show the answer

1 : 8. Make the units the same first: 2 hours = 120 minutes. Then 15 : 120 = 1 : 8.

Divide an amount in a ratio with two or more parts

$170 is shared in the ratio 2 : 3.
How much is the smaller share?

  1. $102
  2. $68
  3. $85
  4. $34
Show the answer

$68. 2 + 3 = 5 parts. One part is 170 ÷ 5 = 34. The smaller share is 2 × 34 = 68.

Expressions, equations and formulae

Letters mean different things in expressions, formulae and equations

Which of these is an EQUATION, where the letter is an unknown to be found?

  1. y = 2x + 1
  2. 3x + 2 = 11
  3. A = lw
  4. 3x + 2
Show the answer

3x + 2 = 11. 3x + 2 = 11: where the letter is an unknown to be found.

The laws and the order of operations in algebra, with squares and cubes

Which is the same as x × 6 × y?

  1. 6 + xy
  2. 6x + y
  3. 6xy
  4. 6x + 6y
Show the answer

6xy. Multiplication can be done in any order (commutative): x × 5 × y = 5xy.

Multiply a bracket by a single term; factorise by the highest common factor

Factorise fully
8y + 28

  1. 8(y + 7)
  2. 2(4y + 7)
  3. 4(2y + 7)
  4. 4(2y + 28)
Show the answer

4(2y + 7). The highest common factor of 8y and 28 is 4. Take it outside: 4(2y + 7).

A situation in words or as an expression with integer or fractional coefficients

A third of a number t, and then 9 is taken away.
Which expression is this?

  1. t/3 − 9
  2. 3t − 9
  3. (t − 9)/3
  4. 9 − t/3
Show the answer

t/3 − 9. A third of t is t/3. Then take 9 away from it: t/3 − 9.

A situation in words or as a formula; change the subject

A phone plan costs $40 a month plus $45 for every gigabyte used.
h is the number of gigabytes and C is the bill in dollars.
Which formula is right?

  1. C = 45h + 40
  2. C = 85h
  3. C = 45(h + 40)
  4. C = 40h + 45
Show the answer

C = 45h + 40. Every one of the gigabytes adds 45, which is 45h. The 40 is paid once, whatever h is: C = 45h + 40.

A situation in words or as an equation; solve it (unknown on either or both sides)

Ben has 8 full boxes of pens and 6 loose pens.
Tom has 2 full boxes and 60 loose pens.
They have the SAME number of pens. How many pens are in a full box?

  1. 7
  2. 9
  3. 5
  4. 54
Show the answer

9. The equation is 8n + 6 = 2n + 60. Take 2n from both sides: 6n + 6 = 60. So 6n = 54 and n = 9.

Letters can stand for open and closed intervals (two terms)

Solve
3x − 3 > −6

  1. x < 1
  2. x > 1
  3. x < −1
  4. x > −1
Show the answer

x > −1. Add 3, then divide by 3. The sign stays the same.

Sequences, functions and graphs

Term-to-term rules and sequences, including fractions

A sequence starts at 2 and the rule is "add 2/3".
What is the 4th term?

  1. 10/3
  2. 3
  3. 4
  4. 14/3
Show the answer

4. 2, 8/3, 10/3, 4: three steps of 2/3 from the start.

nth term rules of the form an ± b

Find the nth term.
4, 13, 22, 31, …

  1. 9n + 4
  2. 9n − 5
  3. 4n + 9
  4. n + 9
Show the answer

9n − 5. It goes up in 9s, so it starts 9n. When n = 1, 9n = 9, and the first term is 4: adjust by −5.

Functions: outputs, and inputs by inverse operations, including fractions

A function machine: input → × 3 → + 4 → output.
The INPUT is 8. What comes out?

  1. 24
  2. 36
  3. 28
  4. 15
Show the answer

28. 8 × 3 = 24, then + 4 = 28.

A situation in words or as y = mx + c

A phone plan costs $27 a month plus $35 for every gigabyte used.
x is the number of gigabytes and y is the bill in dollars.
Which equation is right?

  1. y = 27x + 35
  2. y = 62x
  3. y = 35x + 27
  4. y = 35(x + 27)
Show the answer

y = 35x + 27. Every one of the gigabytes adds 35, which is 35x. The 27 is paid once, whatever x is: y = 35x + 27.

Tables of values and graphs of y = mx + c

A point on the line y = 2x − 3 has x = −1.
What are its coordinates?

  1. (−1, −5)
  2. (−5, −1)
  3. (−1, 1)
  4. (−1, −2)
Show the answer

(−1, −5). Put x = −1 into the equation: y = −5. The point is (−1, −5): x first, then y.

y = mx + c is a straight line with gradient m and y-intercept c

What is the gradient of
y = x + 6?

  1. −1
  2. 6
  3. 7
  4. 1
Show the answer

1. In y = mx + c the gradient is m, the number in front of x: 1.

Graphs with more than one component; what their intersections mean

Gym A costs $30 to join plus $4 a visit. Gym B costs $5 a visit.
Their cost graphs cross at 30 visits. What does the crossing mean?

  1. At 30 visits both gyms cost the same
  2. You must go 30 times
  3. Gym A costs $30
  4. Gym B is cheaper after 30 visits
Show the answer

At 30 visits both gyms cost the same. Where two cost lines cross, the costs are EQUAL: 30 + 4 × 30 = 5 × 30 = $150. After that the lines swap: Gym A (the flatter line) becomes cheaper.

Geometrical reasoning, shapes and measurements

The hierarchy of quadrilaterals

Which quadrilateral has two pairs of equal sides next to each other, and no parallel sides?

  1. kite
  2. square
  3. parallelogram
  4. rhombus
Show the answer

kite. That describes a kite.

π as circumference over diameter; the circumference formula

A circle has diameter 12 cm.
Find its circumference, in terms of π.

  1. 24π cm
  2. 36π cm
  3. 6π cm
  4. 12π cm
Show the answer

12π cm. Circumference = 2πr = 2 × π × 6 = 12π cm.

Miles and kilometres

5 miles is about 8 km.
About how many km is 5 miles?

  1. 8 km
  2. 10 km
  3. 3.125 km
  4. 6 km
Show the answer

8 km. 5 ÷ 5 = 1 lots of 5 miles, each about 8 km: 1 × 8 = 8 km.

Area of parallelograms and trapezia

The questions for this part come with a picture or are played as a game, so they are best tried in Huh Lab.

Euler's formula for vertices, faces and edges

A solid has 8 faces and 18 edges.
Use Euler's formula to find how many vertices it has.

  1. 10
  2. 12
  3. 26
  4. 14
Show the answer

12. Faces + vertices − edges = 2 for every solid like this: 8 + 12 − 18 = 2. So vertices = 18 − 8 + 2 = 12.

Volume of a triangular prism

A prism has a triangular cross-section with
base 6 cm and height 7 cm. It is 3 cm long.
Find its volume.

  1. 16 cm³
  2. 63 cm³
  3. 21 cm³
  4. 126 cm³
Show the answer

63 cm³. Cross-section = ½ × 6 × 7 = 21 cm². Times length 3 = 63 cm³.

Front, side and top views to scale

The questions for this part come with a picture or are played as a game, so they are best tried in Huh Lab.

Surface area of cubes, cuboids, triangular prisms and pyramids

A square-based pyramid has base edges of 8 cm.
Each triangular face has a slant height of 9 cm.
Find its total surface area.

  1. 352 cm²
  2. 208 cm²
  3. 136 cm²
  4. 144 cm²
Show the answer

208 cm². Base: 8 × 8 = 64. Four triangles, each ½ × 8 × 9 = 36: 4 × 36 = 144. Total 208 cm².

A regular polygon has as many lines of symmetry, and the same order of rotation, as sides

A regular polygon has rotational symmetry of order 10.
How many sides does it have?

  1. 20
  2. 12
  3. 10
  4. 36
Show the answer

10. A regular polygon with n sides has n lines of symmetry and rotational symmetry of order n. Here n = 10.

The exterior angle of a triangle equals the two opposite interior angles

The questions for this part come with a picture or are played as a game, so they are best tried in Huh Lab.

Alternate, corresponding and vertically opposite angles

Two parallel lines are crossed by a third line.
One angle is 70°. What is its alternate angle?

  1. 110°
  2. 70°
  3. 20°
  4. 290°
Show the answer

70°. Alternate angles (the Z shape) are equal: 70°.

Position and transformation

Bearings as a measure of direction

The bearing of B from A is 265°.
What is the bearing of A from B?

  1. 265°
  2. 095°
  3. 085°
  4. 090°
Show the answer

085°. Turn round: add 180° if the bearing is under 180°, take 180° away if it is over. 265° − 180° = 085°.

Midpoint of a line segment from coordinates

Find the midpoint of
(−4, 3) and (2, 11).

  1. (7, −1)
  2. (3, 4)
  3. (−2, 14)
  4. (−1, 7)
Show the answer

(−1, 7). Average the x values and the y values: (−1, 7).

Translate points and shapes by a vector

a = (5, 1) b = (5, −1)
Find a + b.

  1. (25, −1)
  2. (4, 6)
  3. (0, 2)
  4. (10, 0)
Show the answer

(10, 0). Add the x parts and the y parts: (5 + 5, 1 + −1).

Reflect in lines on or parallel to the axes and in y = ±x; identify a reflection and its line

The questions for this part come with a picture or are played as a game, so they are best tried in Huh Lab.

A rotation needs a centre, a direction and an angle

The questions for this part come with a picture or are played as a game, so they are best tried in Huh Lab.

Enlarge from a centre outside or on the shape; identify an enlargement and its scale factor

The point (−6, −4) is enlarged with centre (0, 0)
and scale factor 2. Where does it go?

  1. (−6, −8)
  2. (−12, −8)
  3. (−12, −4)
  4. (−4, −2)
Show the answer

(−12, −8). From the origin, multiply BOTH coordinates by 2: (−12, −8).

Statistics

Advantages and disadvantages of sampling methods

50 pupils are chosen so that each year group has the same share of the sample as it has of the school.
Which sampling method is this?

  1. systematic
  2. convenience
  3. random
  4. stratified
Show the answer

stratified. 50 pupils are chosen so that each year group has the same share of the sample as it has of the school. That is stratified sampling: every group is represented in the right proportion.

Record and show data, now including time series and stem-and-leaf diagrams

Score: 1, 2, 3, 4
Frequency: 2, 2, 4, 6
Find the mean score.

  1. 42
  2. 10.5
  3. 3
  4. 2.5
Show the answer

3. Total of score × frequency = 42. Total frequency = 14. 42 ÷ 14 = 3.

Compare two distributions with an average and the range

Test scores.
Class A: mean 61, range 15.
Class B: mean 64, range 8.
Which class did better on average?

  1. It is impossible to tell
  2. Class A
  3. They are the same
  4. Class B
Show the answer

Class B. "On average" means compare the means: 64 is higher, so Class B. The range says nothing about how high the scores were.

Interpret patterns, trends and relationships within and between data sets

The questions for this part come with a picture or are played as a game, so they are best tried in Huh Lab.

Probability

Complementary events have probabilities that total 1

The probability that it rains is 0.45.
What is the probability that it does not rain?

  1. 0.55
  2. 1.45
  3. 0.65
  4. 0.45
Show the answer

0.55. 1 − 0.45 = 0.55.

Tables, diagrams and lists of the outcomes of combined independent events

Two fair coins are tossed.
How many possible outcomes are there?

  1. 6
  2. 4
  3. 2
  4. 3
Show the answer

4. List them: HH, HT, TH, TT. Four, and they are equally likely.

Theoretical probability of equally likely combined events

Two fair coins are tossed.
What is the probability of one head and one tail?

  1. 1/2
  2. 1/4
  3. 3/4
  4. 1/3
Show the answer

1/2. The four equally likely outcomes are HH, HT, TH, TT. One head and one tail happens in 2 of them: 1/2.

The mistakes that cost the most marks

Huh Lab checks every wrong answer against known mistakes like these, and goes back to the step behind the one your child keeps making.

Moves a term across without reversing it

Whatever is done to x must be UNDONE on the other side: + becomes −, × becomes ÷.

Loses the negative sign

Use a number line: below zero the numbers keep counting, in the other direction.

Gives the y-coordinate first

Along the corridor, THEN up the stairs: x comes before y.

Multiplies when it should divide

Dividing by 0.5 asks "how many halves fit?", so the answer gets BIGGER.

Writes the operations in the order they are said, not the order they happen

Ask "what happens to the number FIRST?" Whatever happens first stays together, in brackets if it needs them.

Works left to right, ignoring order of operations

Multiply and divide before adding and subtracting.

Leaves out some of the faces

Count the faces before adding: a cuboid has 6, a closed cylinder has two circles and the curved part.

Puts the decimal point in the wrong place

Estimate first: 3.45 × 6 is about 3 × 6 = 18, so the answer is near 20.

Other Cambridge Lower Secondary Maths stages

Practise it as a game

Short rounds on any topic, a new question every time, the exact mistake found, and a report to you after every session.

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