# RD Sharma Solutions Class 7 Mathematics Solutions for Mensuration 1 Exercise 20.1 in Chapter 20 - Mensuration 1

Question 6 Mensuration 1 Exercise 20.1

A door of dimensions 3 m x 2m is on the wall of dimension 10 m x 10 m. Find the cost of painting the wall if rate of painting is Rs 2.50 per sq. m.

Given length of the door = 3 m

Also given that breadth of the door = 2 m

Side of the wall = 10 m

We know that Area of the square = (Side)^2

Area of the wall = Side x Side = 10 m x 10 m

= 100 m^2

We know that the area of the rectangle = length x breadth

Area of the door = Length x Breadth = 3 m x 2 m = 6 m^2

Thus, required area of the wall for painting = Area of the wall – Area of the door

= (100 – 6) m^2

= 94 m^2

Rate of painting per square metre = Rs. 2.50

Hence, the cost of painting the wall = Rs. (94 x 2.50) = Rs. 235

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