Primary 6 Maths: Surface Area of Cuboids and Cubes

Primary 6 Maths: Surface Area of Cuboids and Cubes — Tutor Lesson Plan

2026-10-27

Tutor lesson-prep guides · Primary maths

Surface-area errors are rarely formula errors; they are a missing face. Flatten the box, number the faces, and nobody leaves one out.

Objectives — the student can explain surface area as the sum of six faces, use 2(lb + lh + bh) and 6a², adjust for an open-top box, and keep cm² separate from cm³.

01 Prerequisites (3-minute check)

If any of these fails, fix it before the lesson starts.

Skill	Quick check	Pass mark
Rectangle area	5 by 4	20 cm²
Order of operations	2 × (20 + 15 + 12)	94
Volume	A 5 by 4 by 3 box	60 cm³

02 Lesson flow (50 minutes)

Time	Stage	Tutor does	Student does
0-8 min	Flatten a box	Cut a box open and lay it flat	Count and number six faces
8-18 min	Cuboid formula	2(lb + lh + bh)	One alone
18-28 min	Cube formula	6a²	One alone
28-38 min	Open top	Subtract one face	One alone
38-46 min	Against volume	Both for the same box	State the two units
46-50 min	Exit check	Three questions marked at once	Finish alone

03 Teaching script (read it out)

Scene 1: Flatten it and count

Open the box: top and bottom, front and back, left and right, six rectangles in all.
Surface area is the sum of those six areas, so 2 × (lb + lh + bh).

Student numbers the faces and pairs the equal ones.

Scene 2: A cube has six equal faces

A cube of edge 6 has 36 cm² per face and 216 cm² in total.
The number can match the volume, but the units never do: cm² against cm³.

Warn: same number, different meaning; always write the unit.

Scene 3: Open top: one face fewer

A 5 by 4 by 3 box without a lid is 94 − 20 = 74 cm².
For boxes, paint and stickers, ask first whether it is open.

Note: read whether it is open at the top or the bottom.

04 Question types and worked steps

Type	Example	Steps	Answer
Cuboid	5 by 4 by 3	2(20 + 15 + 12)	94 cm²
Cube	edge 6	6 × 36	216 cm²
Open top	5 by 4 by 3	94 − 20	74 cm²
Volume for contrast	same box	5 × 4 × 3	60 cm³

Sanity check (teach this): Surface area is usually the larger number for ordinary boxes; if it equals the volume figure, the volume was copied.

05 Independent practice (3 questions)

Question	Answer	What to watch
6 by 5 by 2	104 cm²	Using 2(lb + lh + bh)
Cube of edge 4	96 cm²	Multiplying by 6
5 by 4 by 3, open top	74 cm²	One face subtracted

06 Common mistakes and what to say

Mistake	Student writes	Say this
Only three faces	20 + 15 + 12 = 47	Six faces, in three equal pairs.
cm³ written	answers 94 cm³	Surface area is cm².
Open box not adjusted	answers 94	An open box is missing one 20 cm² face.
Cube multiplied by 4	6 × 4	Six faces, so 6 × side × side.

07 Homework (paper, section and question numbers)

Primary 6 first-term paper — Section C, questions 6 to 8
Primary 6 first-term paper — Section E, questions 10 and 11

08 Exit check (last 5 minutes)

Question	Answer	Decision
6 by 5 by 2	104 cm²	All right: Primary 6 maths complete
Cube of edge 4	96 cm²	One wrong: re-teach ×2 and ×6
5 by 4 by 3, open top	74 cm²	Two wrong: repeat the flattening

09 Tutor FAQ

Must they memorise the formula?

Yes, but flatten first; one flattening prevents the missing-face error.

Cylinder surface area?

Touched on in the second term; this lesson is cuboids and cubes.

Real applications?

Cardboard for a box, paint, wrapping paper: all the same formula.

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A TutorZone lesson-prep guide. Written by the TutorZone team; questions and lesson flow are original and are not taken from any school or publisher material.