The dimensions of a room are (9 m × 8 m × 6.5 m). It has one door of dimensions (2 m × 1.5 m) and two windows,
Question:
The dimensions of a room are (9 m × 8 m × 6.5 m). It has one door of dimensions (2 m × 1.5 m) and two windows, each of dimensions (1.5 m × 1 m). Find the cost of whitewashing the walls at Rs 25 per square metre.
Solution:
Length of the room, l = 9 m
Breadth of the room, b = 8 m
Height of the room, h = 6.5 m
Now,
Area of the walls to be whitewashed
= Curved surface area of the room − Area of the door − 2 × Area of each window
= 2h(l + b) − 2 m × 1.5 m − 2 × 1.5 m × 1 m
= 2 × 6.5 × (9 + 8) − 3 − 3
= 221 − 6
= 215 m2
∴ Cost of whitewashing the walls at Rs 25 per square metre
= Area of the walls to be whitewashed × Rs 25 per square metre
= 215 × 25
= Rs 5,375