Question

Find (1) 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 1by12of the steel actually used was wasted in making the tank.​

Answer 1

)Diameter of a cylindrical(closed) petrol tank=4.2 m

Radius=24.2=2.1 m

Height=4.5 m

Curved Surface area=2πrh=2×722×2.1×4.5=59.4sq.m

(ii)Total surface area=2πr(r+h)=2×722×2.1×(2.1+4.5)=2×722×2.1×6.6=87.12 sq.m

Let the amount of steel used in making the tank=x

Steel wasted=12x

Given:Amount of steel required−Amount of steel wasted=T.S.A of the tank.

⇒x−12x=87.12

⇒1212x−x=87.12

⇒1211x=87.12

⇒x=1112×87.12=95.04sq.m

∴95.04sq.m steel was used in actual while making such a tank.