Find
(i) the lateral or curved surface area of a closed cylindrical petrol storage tank that is 4.2 m in diameter and 4.5 m high.
(ii) how much steel was actually used, if `1/(12)` of the steel actually used was wasted in making the tank

Explanation

(i) Curved surface area =`2pirh=2xx(22)/(7)xx(4.2)/(2)xx4.5=5.9 m^(2)`
(ii)Total steel used =Total surface area (Assuming thickness =0 m)
`=2pir(r+h)`
`=2xxx(22)/(7)xx(4.2)/(2)((4.2)/(2)+4.5)`
`=(44)/(7)xx2.1xx(13.2)/(2)=22xx0.3xx13.2=87.12me^(2)`
Let actural steel used is x `m^(2)`
`(11)/(12)x=87.12`
`x=(87.12xx12)/(11)=95.04 m^(2)`