Nets and surface area
Answers are for parents and teachers.
1
Find the surface area of a cuboid 9 cm by 4 cm by 3 cm.
2 × (36 + 27 + 12) = 2 × 75 = 150 cm².
2
Find the surface area of a cube with edge 7 cm.
6 × 49 = 294 cm².
3
A square pyramid has base 12 cm and slant height 10 cm. Find its surface area.
Base 144. Each triangle 12 × 10 ÷ 2 = 60. Total 144 + 240 = 384 cm².
4
A cuboid is 2 cm by 1 cm by 1 cm. Double all its sides and find both surface areas.
First: 2 × (2 + 2 + 1) = 10 cm². Second (4 by 2 by 2): 2 × (8 + 8 + 4) = 40 cm². It is 4 times bigger.
5
Seif says a cube with surface area 96 cm² has edge 96 ÷ 6 = 16 cm. What did he forget?
16 is the area of one face. The edge is the number that multiplied by itself gives 16: 4 cm.