Question

Find the cost of painting a cuboid of dimensions $20$ cm $\times 15$ cm $\times 12$ cm at the rate of 5 paise per square centimeter

Answer 1

l = 20 cm, b = 15 cm, h = 12 cm.
$\therefore \text{Total surface area of a cuboid}$
$A=2(lb+bh+lh)$
$=2(20\times 15+15\times 12+20\times 12)$
$=2(300+180+240)$
$=2\times 720$
$=1440\text{sq.cm.}$
The cost of painting a cuboid at the rate of 5 paise per sq. cm for 1440 sq.cm.
$=1440\times 5\text{paise}$
= 7200 paise
$=₹\frac{7200}{100}$
$=₹72$