Question

the total surface area of a closed cylindrical petrol storage tank whose diameter is 4.2m.and height 4.5m. is 87.12sq.m
how much steel sheet was actually used , if 1/12 of the steel was wasted in making the tank.

Answer 1

Radius of the tank (r) = 4.2/2 m = 2.1 m
Height of the tank (h) = 4.5 m
Curved surface area = 2πrh m2
= (2 × 22/7 × 2.1 × 4.5) m2
= 59.4 m2
(ii) Total surface area of the tank = 2πr(r + h) m2
= [2 × 22/7 × 2.1 (2.1 + 4.5)] m2
= 87.12 m2

Let x be the actual steel used in making tank.
∴ (1 - 1/12) × x = 87.12
⇒ x = 87.12 × 12/11
⇒ x = 95.04 m2

Answer 2

Answer:

Step-by-step explanation:

Given :-

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

Height of the tank (h) = 4.5 m

To Find :-

Total Surface Area

Formula to be used :-

Curved surface area = 2πrh

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

Solution :-

Putting all the values, we get

⇒ Curved surface area = 2πrh

⇒ Curved surface area = (2 × 22/7 × 2.1 × 4.5)

⇒ Curved surface area = 59.4 m²

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

⇒ Total surface area of the tank = [2 × 22/7 × 2.1 (2.1 + 4.5)]

⇒ Total surface area of the tank = 87.12 m²

Given :-

1/12  of the steel was wasted in making  the tank​.

To Find :-

Steel Required

Solution :-

Let x be the actual steel used in making tank.

⇒ (1 - 1/12) × x = 87.12

⇒ x = 87.12 × 12/11

⇒ x = 95.04 m²

Hence, 95.04 m² of steel required.