The radius of the circular lid of a tank is 1.4 m. How much will it cost to paint both sides of 100 such lids at the rate of Rs 20 per sq m?

Given that, radius of the circular lid of a tank, r = 1.4 m

Now this lid is painted on both sides. So, we need to find area of both sides of the circular lid.

Area of one side = πr²

= 22/7 × 1.4²

= (22 × 1.4 × 1.4)/7

= 43.12/7

= 6.16

Area of both sides = 2 × Area of one side

= 2 × 6.16

= 12.32

So, area painted on both sides of 1 circular lid = 12.32 m²

Then, area painted on both sides of 100 such circular lid = 12.32 × 100 = 1232 m²

Cost of painting 1 m² area = Rs. 20

Cost of painting 1232 m² area = 20 × 1232 = Rs. 24640

Thus, it will cost Rs. 24,640 to paint 100 such lids at the rate of Rs. 20 per m².