Question

It is required to make a closed cylindrical tank of height 1 m and base diameter 140 cm from a metal sheet. How many square metres of the sheet are required for the same ?

Answer 1

Total area of tank = surface area of cylinder + 2 x cross section area of tank
= $2\pi rL+2\pi r^2$
= $2\pi r$ ( L + r)

Given,
diametre of base = 140 cm
radius of base (r) = 70cm
height of tank (L) = 1 m = 100 cm

total area =$2\pi r$ ( L + r)
= 2 x 22/7 x 70 x ( 100 + 70)
= $20\times 22\times 170c{m}^2$
= $74800c{m}^2$
= $7.48m^2$

hence, $7.48m^2$ sheets are required for the making tank