Question

Find the cost of painting of the outer surface of a closed box which is $60cm$ long, $40cm$ broad and $30cm$ high at the rate of $50$ paise per $20c{m}^2$

Answer 1

Length of the box $\left(l\right)=60cm$
Breadth of the box $\left(b\right)=40cm$
Height of the box $\left(h\right)=30cm$
Total surface area of the box $=2(lb\times bh\times hl)$
$=2(60\times 40+40\times 30+60\times 30)c{m}^2$
$=2(2400+1200+1800)c{m}^2$
$=2\times 5400c{m}^2$
$=10800c{m}^2$
Cost of painting $20c{m}^2=50paise=Rs\frac{50}{100}$
$\therefore$ Cost of painting $1c{m}^2=Rs\frac{50}{100}\times \frac{1}{20}$
$\therefore$ Cost of painting $10800c{m}^2=Rs\frac{50}{100}\times \frac{1}{20}\times 10,800=Rs270$