Question

find the volume of a cylinder which is formed by revolving plastic sheet of dimensions 14cm ×7cm along its length

Answer 1

Here, CSA of cylinder is given i.e. the revolved part.

CSA of cylinder = 14 × 7

= 98 sq cm

$2\pi \: rh \: = 98$

2 × 22/7 × r × h = 98

Now, since it is revolved along its length, height = 14 cm

2 × 22/7 × r × 14 = 98

44 × r = 49

r = 49/44 cm

Now, volume of cylinder

$\pi \: r {}^{2} h$

= 22/7 × (49/44)^2 × 14

= 343 / 88 x 14

= 3.89 x 14

= 54.56 cm^3

Hope this helps!