What is the most common mistake in semicircle area?

Putting the diameter in place of the radius; halve the diameter before squaring.

How does a semicircle perimeter differ from a circumference?

Circumference is 3.14 × diameter; a semicircle perimeter is half of it plus one diameter.

How is the diameter set when two circles are cut from a rectangle?

Each diameter equals the shorter side, with the two circles side by side along the long side.

P6 Maths Composite Shapes Paper 4: Error Review

2026-11-09

Tutor Prep Guide · P6 Maths

Ten original items, each with an answer and a one-line explanation.

Direct answers　Items 1-3 are basic, 4-6 intermediate and 7-9 challenge, with item 10 as the error review. Time yourself first, then check every answer and redo the wrong ones.

01　Paper details (check answers afterwards)

Item	Detail
Questions	10
Suggested time	20
Difficulty mix	Foundation 3 · Intermediate 3 · Challenge 3 · Error redo 1
Chapter	Chapter: P6 Maths Composite Shapes with Circles
Level	P6

02　Questions (10 items)

FoundationA semicircle has diameter 18 cm. Find its area. (Take pi = 3.14)
FoundationFind the area of a quarter circle of radius 10 cm.
FoundationA semicircle has diameter 6 cm. Find its perimeter, including the diameter.
IntermediateA ring has outer radius 8 cm and inner radius 3 cm. Find its area.
IntermediateA square has side 14 cm and contains its largest inscribed circle. Find the area outside the circle.
IntermediateFind the perimeter of a quarter circle of radius 6 cm.
ChallengeTwo concentric circles have radii 10 cm and 7 cm. Find the area between them.
ChallengeA semicircular lawn has diameter 20 m. Turf costs 25 dollars per square metre. Find the total cost.
ChallengeA card 16 cm by 8 cm has two largest possible circles cut out. Find the remaining area.
Error redoError review: a pupil gives 3.14 × 16 = 50.24 cm as the perimeter of a semicircle of diameter 16 cm. What is the correct perimeter?

03　Answers and one-line notes

#	Answer	One-line note
1	127.17 cm²	The radius is 9 cm, so 3.14 × 81 ÷ 2 = 127.17 cm².
2	78.5 cm²	3.14 × 100 ÷ 4 = 78.5 cm².
3	15.42 cm	3.14 × 6 ÷ 2 = 9.42 cm, and adding 6 cm gives 15.42 cm.
4	172.7 cm²	3.14 × (64 − 9) = 3.14 × 55 = 172.7 cm².
5	42.14 cm²	196 − 3.14 × 49 = 196 − 153.86 = 42.14 cm².
6	21.42 cm	The arc is 2 × 3.14 × 6 ÷ 4 = 9.42 cm, and two radii add 12 cm, giving 21.42 cm.
7	160.14 cm²	3.14 × (100 − 49) = 3.14 × 51 = 160.14 cm².
8	3925 dollars	The area is 3.14 × 100 ÷ 2 = 157 m², and multiplying by 25 gives 3925 dollars.
9	27.52 cm²	Each circle has diameter 8 cm and radius 4 cm, so together they take 100.48 cm² and 27.52 cm² remains.
10	41.12 cm	Halve the circle first, then add the diameter: 3.14 × 16 ÷ 2 + 16 = 41.12 cm.

04　What to do after marking

After marking, redo only the wrong items and write down which step went wrong (formula, unit, or misread number).
Repeat the same item two days later; move to the next paper only when both attempts are correct.
Parents only need the answer and note columns; there is no need to explain every item.

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