Q2 of 26 Page 183

If the cost of making a leather ball is 431.20 at 17.50 per square cm., let us write by calculating the length of diameter of the ball.

Given:


Cost of making a leather ball = Rs.431.20


Cost per square cm = Rs.17.50


Formula used:


1. Cost of making a leather ball = Surface Area of ball × Cost per square cm


⇒ 431.20 = Surface area × 17.50


⇒ Surface Area = 24.64 cm2


2. surface area of sphere = 4×π×r2



⇒ 4×π×r2 = 24.64


⇒ r2 = 1.96


⇒ r = 1.4cm


So, the diameter of sphere = 2×Radius = 2.8cm


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