A classroom is 7 m long, 6 m broad and 3.5 m high. Doors and windows occupy an area of 17 m². What is the cost of white washing the walls at the rate of Rs. 1.50 per m²?

Given: Length of classroom = 7 m

Breadth of classroom = 6 m

Height of classroom = 3.5 m

To find: The cost of whitewashing.

Formula Used:

Area of rectangle = length × breadth

Explanation:

Area of four walls (including doors & windows) = 2(l × h + b × h)

= 2(7 × 3.5 + 6 × 3.5)

= 91 m²

Then,

Area of walls without doors & windows = area including doors & windows – area occupied by doors & windows

Area of only walls = 91 – 17 = 74 m²

So,

Cost of white washing 1 m² area of walls = Rs.1.50

∴ Total cost of white washing = 74 × 1.50 = Rs.111