A door of length 2 m and breadth 1m is fitted in a wall. The length of the wall is 4.5 m and the breadth is 3.6 m (Fig11.6) Find the cost of white washing the wall, if the rate of white washing the wall is ₹ 20 per m² 

Given that,  A door of length 2 m and breadth 1m is fitted in a wall and the length of the wall is 4.5 m and the breadth is 3.6 m.

Area of wall = Length $\times$ Breadth

= 4.5 $\times$ 3.6

= 16.2 m²

Area of door = Length $\times$ Breadth

= 2 $\times$ 1

= 2 m²

Thus,  area of the wall for whitewash = Area of the wall - Area of the door

= 16.2 - 2

= 14.2 m²

Now it is given that, The rate of whitewashing the wall = ₹ 20 per m²

Hence, The cost of whitewashing 14.2 m² wall = 14.2 $\times$ 20 = ₹ 284.