Find:
(i) the lateral or curved surface area of a closed cylindrical petrol storage tank that is 4.2 m in diameter and 4.5m high.
(ii) How much steel was actually used if 1/12 of the steel actually used was wasted in making the tank. (Assume π = 22/7)
Height of cylindrical tank, h = 4.5m
Radius of the circular end , r = (4.2/2)m
= 2.1m
(i) the lateral or curved surface area of cylindrical tank is 2πrh
= 2 × (22/7) × 2.1 × 4.5 m2
= (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 × (22/7) × 2.1 × (2.1 + 4.5)
= 44 × 0.3 × 6.6
= 87.12 m2
Now, Let S m2 steel sheet be actually used in making the tank.
S(\(1 - \frac{1}{12}\)) = 87.12 m2
This implies, S = 95.04 m2
Therefore, 95.04 m2 steel was used in actual while making such a tank.