Q9 of 20 Page 225

Find

(i) The total surface area of a closed cylindrical petrol storage tank whose diameter 4.2 m. and height 4.5 m.


(ii) How much steel sheet was actually used, if of the steel was wasted in making the tank.

(i) Given, diameter = 4.2m

Radius = 2.1m


Height = 4.5m


Total surface area = 2πr(r + h)


= 2 × 3.14 × 2.1 × (2.1 + 4.5)


= 87m2


(ii) if of the steel was wasted in making the tank. The sheet used in making the tank = (1−) × 87


= × 87


= 79.75m2


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