Question

Find the lateral surface area and the total surface area of a cuboid of dimensions 40 cm × 30 cm × 20 cm.

Answer 1

Here, l = 40 cm, b = 30 cm, h = 20 cm

Lateral surface area of the cuboid = $2\left(l+b\right)\times h$
$$\begin{gathered} =2\left(40+30\right)\times 20 \\ =2\times 70\times 20 \\ =2800{\mathrm{cm}}^2 \end{gathered}$$

∴ Total surface area of the cuboid = $2\left(lb+bh+lh\right)$
$$\begin{gathered} =2\left(40\times 30+30\times 20+40\times 20\right) \\ =2\left(1200+600+800\right) \\ =2\times 2600 \\ =5200{\mathrm{cm}}^2 \end{gathered}$$