Question

A room is 5 metres long, 4 metres broad and 3 metres high. Find the area of the four walls. Also find the area of the ceiling and the area of the floor. If it costs ₹ 0.30 to whitewash 1 dm${}^2$ of wall, find the cost of whitewashing the four walls and the ceiling.

Answer 1

Area of four walls $=lh+bh+lh+bh=2h(l+b)=6\times 9m^2=54m^2$
Area of ceiling = Area of floor = 20 $m^2$
$\text{Since}1m^2=100d{m}^2,$
$\therefore 54m^2=5400d{m}^2\text{and}20m^2=2000d{m}^2$
Cost of whitewashing the four walls at the rate of ₹ 0.30 per $d{m}^2$$=₹(5400\times 0.30)=₹1620$
Cost of whitewashing the ceiling at the rate of ₹ 0.30 per $d{m}^2$$=₹(2000\times 0.30)=₹600$
$\text{Total cost of white washing}=₹1620+₹600=₹2220$