# 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. - Mathematics

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.

["Assume "pi=22/7]

#### Solution

Height (h) of cylindrical tank = 4.5 m

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

(i) Lateral or curved surface area of tank = 2πrh

=(2xx22/7xx2.1xx4.5)m^2

= (44 × 0.3 × 4.5) m2

= 59.4 m2

Therefore, CSA of tank is 59.4 m2.

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

=[2xx22/7xx(2.1+4.5)]m^2

= (44 × 0.3 × 6.6) m2

= 87.12 m2

Let A m2 steel sheet be actually used in making the tank.

therefore(1-1/12)=87.12m^2

rArr A=(12/11xx87.12)m^2

⇒ A = 95.04 m2

Therefore, 95.04 m2 steel was used in actual while making such a tank.

Concept: Surface Area of Cylinder
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#### APPEARS IN

NCERT Class 9 Maths
Chapter 13 Surface Area and Volumes
Exercise 13.2 | Q 9 | Page 217