Question

Find the lateral curved surface area of a cylinderical petrol storage tank that is 4.2 m in diameter and 4.5 m high. How much steel was actually used, if `1/12` of steel actually used was wasted in making the closed tank? 

Answer 1

Height (h) cylindrical tank=4.5m 

Radius (r) of circular end of cylindrical tank =` 4.2/2m=2.1 m` 

(1) Lateral or curved surface area of tank = `2pirh` 

⇒` 2xx3.14xx2.1xx4.5m^2` 

= `59.4m^2` 

(2) Total surface area of tank = `2pir(r+h)` 

⇒ `2[22/7]xx2.1(2.1+4.5)m^2` 

= `87.12m^2` 

Let  A ` m^2` steel sheet be actually used in making the tank 

`∴ A(1-1/12)=87.12m^2` 

⇒ `A= (12/pixx87.12)m^2` 

⇒ `A=95.04m^2` 

Thus, ` 95.04m^2` steel was used in actual while making the tank.