How do the cube and cuboid formulas differ?

A cube has six equal faces, so 6 × edge²; a cuboid uses 2 × (lw + lh + wh).

How many faces does an open box lose?

One, the top; the base and four sides remain.

Why does cutting add surface area?

Each cut exposes two new faces.

Surface Area — Practice Paper 2 (10 items with answers)

2026-10-29

Tutor Prep Guide · Primary Maths

Paper 2 adds working backwards and cutting: from a surface area back to an edge or a height, and why cutting increases the total surface area.

Direct answer　Surface area is the sum of all six faces; for a cuboid, 2 × (lw + lh + wh).

01　Paper details (check answers afterwards)

Item	Detail
Questions	10 items
Suggested time	About 20 minutes
Difficulty mix	Foundation 3 · Intermediate 3 · Challenge 3 · Error redo 1
Chapter	Chapter: Primary 6 Maths: Surface Area — Tutor Lesson Plan
Level	Primary 6

02　Questions (10 items)

FoundationA cube has edge 2 cm. Find its surface area.
FoundationA cuboid is 7 cm long, 4 cm wide and 3 cm high. Find its surface area.
FoundationA cube has edge 5 cm. Find its surface area.
IntermediateA cuboid is 10 cm long, 6 cm wide and 4 cm high. Find its surface area.
IntermediateAn open tank is 9 cm long, 7 cm wide and 5 cm high. Find its surface area.
IntermediateA cube has surface area 216 cm². Find its edge.
ChallengeA cuboid has surface area 148 cm², length 6 cm and width 4 cm. Find its height.
ChallengeA cube of edge 4 cm is cut into eight cubes of edge 2 cm. How many times the original surface area is the total now?
ChallengeA classroom is 8 m long, 6 m wide and 3 m high. Only the four walls are painted. How many m² is painted?
Error redoA cube has edge 7 cm. Find its surface area. (Common error: working out 6 × 7.)

03　Answers and one-line notes

#	Answer	One-line note
1	24 cm²	Each of the six faces is 2 × 2 = 4 cm², so 6 × 4 = 24 cm².
2	122 cm²	2 × (28 + 21 + 12) = 2 × 61 = 122 cm².
3	150 cm²	One face is 25 cm², so six faces give 6 × 25 = 150 cm².
4	248 cm²	2 × (60 + 40 + 24) = 2 × 124 = 248 cm².
5	223 cm²	The base is 63 cm² and the four sides are 2 × 45 + 2 × 35 = 160 cm², giving 223 cm².
6	6 cm	One face is 216 ÷ 6 = 36 cm², so the edge is 6 cm.
7	5 cm	Half the surface area is 74 cm²; 74 − 24 = 50, and 50 ÷ (6 + 4) = 5 cm.
8	2 times	The original is 6 × 16 = 96 cm²; eight small cubes give 8 × 24 = 192 cm², i.e. 2 times.
9	84 m²	2 × 8 × 3 = 48 m² plus 2 × 6 × 3 = 36 m² gives 84 m², excluding ceiling and floor.
10	294 cm²	One face is 7 × 7 = 49 cm², so 6 × 49 = 294 cm²; never multiply the edge alone.

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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Questions and answers are written originally by the TutorZone team and are not taken from any school, publisher or examination authority paper. Every value is checked by computer.