Question:
Find the surface area of a chalk box, whose length, breadth and height are 18 cm, 10 cm and 8 cm respectively.
Solution:
Length $=18 \mathrm{~cm}$
Breadth $=10 \mathrm{~cm}$
Height $=8 \mathrm{~cm}$
$\therefore$ Total surface area $=2(l b+l h+b h)=2(18 \times 10+18 \times 8+10 \times 8)=2(180+144+80)=808 \mathrm{~cm}^{2}$