Question

A wall is 4.5 m long and 3 m high. It has two equal windows, each having form and dimensions as shown in Fig. 37. Find the cost of painting the wall (leaving windows) at the rate of Rs 15 per m₂.

Answer 1

We have,
Length of a wall = 4.5 m
Breadth of the wall =3 m
Area of the wall = Length x Breadth = 4.5 m x 3 m = 13.5 m²
From the figure we observed that,
Area of the window = Area of the rectangle + Area of the triangle
= (0.8 m x 0.5 m) + ($\frac{1}{2}$ x 0.8 m x 0.2 m) [Since 1 m = 100 cm]
= 0.4 m² + 0.08 m² = 0.48 m²
Area of two windows = 2 x 0.48 = 0.96 m²
Area of the remaining wall (leaving windows ) = (13.5 − 0.96 )m² = 12.54 m²
Cost of painting the wall per m² = Rs. 15
Hence, the cost of painting on the wall = Rs. (15 x 12.54) = Rs. 188.1
(In the book, the answer is given for one window, but we have 2 windows.)