Question

The cost of papering the wall of a room, 12 m long, at the rate of Rs. 1.35 per square meter is Rs. 340.20. The cost of matting the floor at Re. 0.85 per square metre is Rs. 91.80. Find the height of the room

Answer 1

Let the length of room = l = 12 m
breadth of room = b m
height of room = h m

Cost of matting the floor @ Re. 0.85 per m² = Rs. 91.80
floor area = 91.80 / 0.85 = 108 m²
⇒ l × b = 108
⇒ 12 × b = 108
⇒ b = 108/12
⇒ b = 9 m

cost of papering wall @ Rs. 1.35 per m² = Rs. 340.20
wall area is the lateral surface area.
wall area = lateral surface area = 340.20 / 1.35 = 252 m²
⇒ 2h(l+b) = 252
⇒ 2h(12+9) = 252
⇒ 2h×21 = 252
⇒ h = 252/(2×21) 
⇒ h = 6 m

Height of room is 6m.