Q7 of 20 Page 225

The diameter of a roller is 84 cm and its length is 120 cm. It takes 500 complete revolutions to roll once over the play ground to level. Find the area of the play ground in m2.

Given, diameter = 84cm = 0.84m i.e r = 0.42m

Length h = 120cm = 1.20m


Number of revolutions n = 500


Area of the playground = n × curved surface area of the roller


= 500 × 2πrh


= 500 × 2 × 3.14 × 0.42 × 1.2


= 1582.56m2


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