Find
(i) The lateral or curved surface area of a closed cylindrical petrol storage tank that is4.2 m in diameter and 4.5 m high.
(ii) How much steel was actually used, if
of the steel actually used was wasted in making the tank
Height (h) of cylindrical tank = 4.5 m
Radius (r) = (
) = 2.1 m
(i) Lateral or curved surface area of tank = 2πrh
= 2 * 
* 2.1 * 4.5
= (44 × 0.3 × 4.5) m2
= 59.4 m2
Therefore, CSA of tank is 59.4 m2
(ii) Total surface area of tank = 2πr (r + h)
= 2 * 
* 2.1 * (2.1 + 4.5) m2
= (44 × 0.3 × 6.6) m2
= 87.12 m2
Let x m2 steel sheet be actually used in making the tank
x (1 - 
) = 87.12 m2
x = (
* 87.12) m2
x = 95.04 m2
Therefore, 95.04 m2 steel was used in making such a tank
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