Topics › KS3 › Number

Percentages of amounts

pct-01 Present from here

Find $10\%$ of £60.

Option A: £50

Option B: £600

Option C: £6

Option D: £10

Answer and misconceptions

Option A: £50 ✗
Subtracts the percentage as a numberHas done £60 − 10 instead of finding 10%.

Option B: £600 ✗
Multiplies by 10 instead of dividingKnows 10 is involved but has done 60 × 10.

Option C: £6 ✓ Correct

Option D: £10 ✗
Thinks 10% is always 10Treats the percentage as a fixed amount, not a part of £60.
pct-02 Present from here

Find $25\%$ of $80$.

Option A: $20$

Option B: $55$

Option C: $3.2$

Option D: $40$

Answer and misconceptions

Option A: $20$ ✓ Correct

Option B: $55$ ✗
Subtracts 25 from the amountHas done 80 − 25 = 55.

Option C: $3.2$ ✗
Divides the amount by the percentageHas done 80 ÷ 25 = 3.2.

Option D: $40$ ✗
Thinks 25% is a halfConfuses 25% with 50% and halves 80.
pct-03 Present from here

Increase £40 by $15\%$.

Option A: £55

Option B: £60

Option C: £6

Option D: £46

Answer and misconceptions

Option A: £55 ✗
Adds the percentage as an amount of moneyHas done £40 + £15.

Option B: £60 ✗
Uses 1.5 as the multiplier for 15%Has done 40 × 1.5 = 60 (that is a 50% increase).

Option C: £6 ✗
Finds the increase but does not add it onHas worked out 15% of £40 = £6 and stopped.

Option D: £46 ✓ Correct
pct-04 Present from here

What is $1\%$ of $350$?

Option A: $35$

Option B: $3.5$

Option C: $0.35$

Option D: $349$

Answer and misconceptions

Option A: $35$ ✗
Divides by 10 to find 1%Has found 10% instead of 1%.

Option B: $3.5$ ✓ Correct

Option C: $0.35$ ✗
Divides by 1000 to find 1%Has moved the digits three places instead of two.

Option D: $349$ ✗
Subtracts 1 from the amountTreats 1% as the number 1 and takes it away.
pct-05 Present from here

Which single multiplier decreases an amount by $5\%$?

Option A: $\times 0.5$

Option B: $\times 1.05$

Option C: $\times 0.95$

Option D: $\times 0.05$

Answer and misconceptions

Option A: $\times 0.5$ ✗
Thinks 5% as a decimal is 0.5Writes 5% as 0.5 instead of 0.05.

Option B: $\times 1.05$ ✗
Uses the increase multiplier for a decrease× 1.05 increases by 5%.

Option C: $\times 0.95$ ✓ Correct

Option D: $\times 0.05$ ✗
Finds the 5% itself, not the amount left× 0.05 gives the decrease, not the new amount (95%).