Question

Find

(1) The total surface area of a closed cylindrical petrol storage tank whose diameter
4.2 m. and height 4.5 m.
(i) How much steel sheet was actually used, if 1/12
of the steel was wasted in making
of the tank. (anewer quickly and steps in order )​

Answer 1

The amount of steel used = 94.38
`m^(2)`

Explanation:

Height of the tank = 4.5 m.

Diameter of the tank = 4.2 m.

But,

radius =
`(diameter)/(2)`

=
`(4.2)/(2)`

radius = 2.1 m

Total surface area of a cylinder = 2
`\pi`rh + 2
`\pi`
`r^(2)`

= 2
`\pi`r(r + h)

= 2 x
`(22)/(7)` x 2.1 (2.1 + 4.5)

= 44 x 0.3 (6.6)

= 87.12

Total surface area of a cylinder = 87.12
`m^(2)`

Since
`(1)/(12)` of the steel was wasted, then;

`(1)/(12)` x 87.12 = 7.26
`m^(2)`

Actual area of steel sheet used = 87.12 + 7.26

= 94.38
`m^(2)`

Thus, 94.38
`m^(2)` of steel was used in making the tank.