Estimate, add and subtract integers
33 − 51 = ?
- 18
- −84
- 84
- −18
Show the answer
−18. Start at 33 and count down 51: you land on −18.
Huh Lab Maths › Cambridge Lower Secondary Maths › Stage 7
Stage 7 of the Cambridge Lower Secondary Mathematics (0862) curriculum framework, usually Year 7 (ages 11 to 12). Here is what each part asks, a practice question for each, and the mistakes that cost the most marks.
Each part with one practice question, made by the same engine your child plays.
33 − 51 = ?
−18. Start at 33 and count down 51: you land on −18.
(2 + 8) × 3 = ?
30. Brackets first: 2 + 8 = 10. Then 10 × 3 = 30.
16 ÷ (−4) = ?
−4. 16 ÷ 4 = 4. The signs are different, so the answer is negative. −4.
Find the LCM of 12 and 15.
60. Multiples of 15: the first one that 12 also divides is 60.
Which of these is a factor of 616?
11. 616 divides by 11 because the alternating sum of its digits is 0 or a multiple of 11: 616 ÷ 11 = 56.
15² = 225.
So what is √225?
15. Squaring and taking the square root undo each other: 15² = 225, so √225 = 15.
0.31 × 1,000 = ?
310. Multiplying by 1,000 moves each digit 3 places to the left.
Round 17.717 to 2 decimal places.
17.72. Keep 2 digits after the point and look at the next one, 7: it rounds up. 17.72.
Write 7/10 as a percentage.
70%. 7/10 = 70/100 = 70%.
1/6 + 3/4 = ?
(simplest form)
11/12. Use 24 as the denominator: 4/24 + 18/24 = 11/12.
1/3 ÷ 5/6 = ?
2/5. Flip the second fraction and multiply: 1/3 × 6/5 = 2/5.
Work out 5 × 20 × 20 the easy way.
2000. Multiplying can be done in any order: 5 × 20 = 100 first, then 100 × 20 = 2000.
What is 15% of 1160?
174. 10% of 1160 is 116 and 5% is 58. Build 15% from those: 174.
Which statement is true?
7.5 > 7.44. Write both with two decimal places: 7.50 and 7.44. 7.5 is bigger, even if it has fewer digits.
8.9 − −1.7 = ?
10.6. Taking away a negative is the same as adding: 8.9 + 1.7 = 10.6.
0.4 × 0.7 = ?
0.28. 4 × 7 = 28. Two decimal places in the question, so 0.28.
y is inversely proportional to x.
When x = 3, y = 8.
Find y when x = 8.
3. y = k ÷ x. From the first pair, k = 8 × 3 = 24. So y = 24 ÷ 8 = 3.
Drink A mixes juice and water 3:5. Drink B mixes them 4:2.
Which drink is MORE juicy?
Drink B. Compare the share that is juice: A is 3/8 = 37.5%, B is 4/6 = 66.7%. Drink B has more juice.
$30 is shared in the ratio 1 : 4.
How much is the larger share?
$24. 1 + 4 = 5 parts. One part is 30 ÷ 5 = 6. The larger share is 4 × 6 = 24.
In y = 2x + 1, what is the letter x?
A variable: it can take many values. An EQUATION like 3x + 2 = 17 has one answer: x is an unknown to find. A FORMULA like y = 2x + 1 links two quantities: x can be anything, and y follows.
Which is the same as x × 7 × y?
7xy. Multiplication can be done in any order (commutative): x × 5 × y = 5xy.
Expand
2n(2n − 2)
4n² − 4n. Multiply BOTH terms inside by 2n: 2n × 2n = 4n², and 2n × 2 = 4n.
Aisha has p stickers.
They are shared equally between 3 friends, and then each friend gets 4 more.
Which expression is one friend's number?
p/3 + 4. Sharing between 3 is p/3. Then 4 more each: p/3 + 4.
A regular shape has 6 equal sides, each s cm long.
Which formula gives its perimeter P?
P = 6s. 6 sides of s cm each: P = 6 × s = 6s.
I think of a number.
I multiply it by 5 and then add 4.
The answer is 14. What was my number?
2. The equation is 5n + 4 = 14. Take 4 away: 5n = 10. Divide by 5: n = 2.
How many integers satisfy
−2 < x ≤ 1 ?
3. From −1 up to 1: that is 3 integers. < leaves the end number out, ≤ keeps it.
3, 10, 17, 24, …
Which is the term-to-term rule?
add 7. Each term is 7 more than the one before: 3 + 7 = 10, 10 + 7 = 17.
Find the nth term.
1, 6, 11, 16, …
5n − 4. It goes up in 5s, so it starts 5n. When n = 1, 5n = 5, and the first term is 1: adjust by −4.
A function machine: input → × 6 → + 2 → output.
The OUTPUT is 20. What was the input?
3. Run the machine backwards, undoing each step in reverse: 20 − 2 = 18, then ÷ 6 = 3.
A plumber charges C = 8h + 9, where h is the number of hours.
What does the formula say in words?
$9 to come out, plus $8 for every hour. The 8 is multiplied by h, so it is paid for EACH hour. The + 9 is paid once, whatever the hours.
A point on the line y = x + 2 has x = 3.
What are its coordinates?
(3, 5). Put x = 3 into the equation: y = 5. The point is (3, 5): x first, then y.
Which point lies on the line x = 1?
(1, −1). Every point on x = 1 has x-coordinate 1, whatever the other one is. (1, −1) does.
On a graph of water in a bath against time, the line goes DOWN.
What does that show?
Water is going out: the bath is emptying. Read the axes first. Flat means no change; steeper means faster change; going down means the quantity is getting smaller.
A regular polygon has rotational symmetry of order 8.
How many sides does it have?
8. A regular polygon with n sides has n lines of symmetry and rotational symmetry of order n. Here n = 8.
Triangles ABC and PQR are congruent:
A matches P, B matches Q and C matches R.
AB = 6 cm, BC = 7 cm and AC = 8 cm. How long is QR?
7 cm. Congruent shapes are identical, so matching sides are equal. QR matches BC: 7 cm.
The radius of a circle is 12 cm.
How long is its diameter?
24 cm. A diameter is two radii: 2 × 12 = 24 cm.
Convert 5 litres to cm³.
5,000. 1 litre = 1000 cm³. 5 × 1,000 = 5,000.
A triangle has base 40 cm and height 22 cm.
What is its area?
440 cm². Area = ½ × base × height = ½ × 40 × 22 = 440 cm².
A solid has 6 faces, 10 edges and 6 vertices.
Which solid could it be?
pentagonal pyramid. A pentagonal pyramid has 6 faces, 10 edges and 6 vertices. (square-based pyramid: 5, 8, 5.)
A cuboid measures 3 cm by 4 cm by 11 cm.
Find its volume.
132 cm³. 3 × 4 × 11 = 132 cm³.
The questions for this part come with a picture or are played as a game, so they are best tried in Huh Lab.
Find the total surface area of a 9 cm by 2 cm by 2 cm cuboid.
80 cm². Three different faces: 18, 18 and 4 cm². There are two of each: 2 × 40 = 80 cm².
The questions for this part come with a picture or are played as a game, so they are best tried in Huh Lab.
The questions for this part come with a picture or are played as a game, so they are best tried in Huh Lab.
The questions for this part come with a picture or are played as a game, so they are best tried in Huh Lab.
Two parallel lines are crossed by a third line.
One angle is 115°. What is its alternate angle?
115°. Alternate angles (the Z shape) are equal: 115°.
A map has a scale of 1 : 100,000.
A road is 4 km long. How long is it on the map?
4 cm. 4 km = 400,000 cm. Divide by 100,000: 4 cm on the map.
Find the distance between (−6, −3) and (7, −3).
13. The y-coordinates are the same, so the points are on a line across the page. The distance is the gap in the OTHER coordinate: 7 − (−6) = 13.
A translation takes P (8, 4) to (10, 9).
Where does the same translation take Q (9, 5)?
(11, 10). P moved 2 in x and 5 in y. Every point moves the same way, so Q goes to (11, 10).
The point (3, 5) is
reflected in the line y = x.
Where is its image?
(5, 3). x and y swap places.
The point (4, −1) is
rotated 180° about the origin.
Where is its image?
(−4, 1). Both coordinates change sign.
The point (6, 2) is enlarged with centre (0, 0)
and scale factor 2. Where does it go?
(12, 4). From the origin, multiply BOTH coordinates by 2: (12, 4).
Which statement about samples is true?
A larger sample gives results closer to the whole population, but costs more time and money.. Bigger samples are more reliable, but there is a trade-off: they take longer and cost more. That is why a sample is used at all, instead of asking everyone.
The questions for this part come with a picture or are played as a game, so they are best tried in Huh Lab.
A shop wants to know which shoe size to stock most of.
Which average is most suitable?
The mode. It is the size most people wear; the mean could be a size nobody wears.
The questions for this part come with a picture or are played as a game, so they are best tried in Huh Lab.
An event has probability 0.9.
In words, it is…
likely. Probability runs from 0 (impossible) through ½ (an even chance) to 1 (certain).
Where on the probability scale from 0 to 1 is an event that is likely?
0.8. Probabilities run from 0 (impossible) to 1 (certain), with 0.5 an even chance in the middle.
A fair dice is rolled once.
Which list shows ALL the possible outcomes?
1, 2, 3, 4, 5, 6. A dice can show any of 1, 2, 3, 4, 5 or 6, and nothing else. Those six outcomes are equally likely.
A bag holds 3 red and 1 blue balls.
One is picked at random.
What is the probability it is red?
3/4. 3 red out of 4 balls altogether: 3/4.
Huh Lab checks every wrong answer against known mistakes like these, and goes back to the step behind the one your child keeps making.
Use a number line: below zero the numbers keep counting, in the other direction.
< and > leave the end number OUT. ≤ and ≥ keep it in. Check each end separately.
Along the corridor, THEN up the stairs: x comes before y.
A reflection goes straight ACROSS the mirror line, never along it.
Lengths × 3 means areas × 9 and volumes × 27. Square or cube the scale factor.
Quarters plus quarters are still quarters. Only the tops are added.
A triangle is half of the rectangle around it.
The angle is a share of 360°. Turn it into a fraction of the whole first.
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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