Question

ung surface in the system.
9. 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.
(i) how much steel was actually used, if of the steel actually used was wasted in
12
making the tank.
12​

Answer 1

Step-by-step explanation:

Here, r = 4. 2/ 2  m = 2.1 m, h = 4.5 m

 (i) Curved surface area of the storage tank = 2πrh

= 2 × 22 7 × 2.1 × 4.5 m2 = 59.4 m2 Ans.  

(ii) Total surface area of the tank = 2πr (h + r)

= 2 × 22/ 7 × 2.1 (4.5 + 2.1) m2

= 44 × 0.3 × 6.6 m2 = 87.12 m2

Let the actual area of steel used be x m²  

Area of steel wasted = 1/ 12 of x m²  = x/ 12 m² . ... (i)  

∴ area of the steel used in the tank =( x − x /120 )m²

= 11/ 12 x m²

 ⇒ 87.12 = 11/ 12 x  

⇒ x = 87. 12x 12/ 11 = 95.04 m²

 Hence, 95.04 m² of steel was actually used Ans

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