Question

A door of length 2 m and breadth 1 m and a square window
of dimension 0.3 m is fitted in a wall. The length of the wall
is 4.5 m and the breadth is 3.6 m, find the cost of
whitewashing the wall, at the rate of Rs 20 per sq. m.

Answer 1

Analysis

In this question, we first have to find the total area of the wall and the subtract the sum of the areas of the door and window from it. This is the area that can be whitewashed. Then multiply the area with the rate provided and hence we can derive the answer.

Solution,

→ The Wall

Length = 4.5 m

Breadth = 3.6 m

Area = lb

= 4.5 x 3.6

= 16.2 m²

→ The Door

Length = 2 m

Breadth = 1 m

Area = lb

= 2 x 1

= 2 m²

→ The Window

Side = 0.3 m

Area = a²

= 0.3 x 0.3

= 0.09 m²

→ Area that can be whitewashed

= Total area of wall - [Area of door + Area of window]

= 16.2 - [2-0.09]

= 16.2 - 1.91

= 14.29 m²

→ Cost of Whitewashing

Rate of whitewashing 1 m² = Rs. 20

Cost of whitewashing 14.29 m² = 14.29 x 20

= Rs. 285.80

∴ A sum of Rs. 285.80 must be paid to whitewash the wall.