WAEC 2020 · Paper 1 · Q18

A solid cuboid has a length of $7\text{ cm}$ , a width of $5\text{ cm}$ and a height of $4\text{ cm}$ . Calculate its total surface area.

Worked solution (try it first)

A cuboid has three pairs of equal faces: $7 \times 5 = 35$ , $7 \times 4 = 28$ and $5 \times 4 = 20$ .
Total surface area: $2(35 + 28 + 20) = 2 \times 83$
$= 166\text{ cm}^2$ , option B.