Question

The difference between the outer curved surface and the inner curved surface area of a hollow cylinder is 352 cm². If its height is 28 cm and volume of the material in its is 704 cm³, then find its internal curved surface area.

Answer 1

Given:

Difference between outer and inner curved surface areas = 352 cm²

Height h = 28cm

Volume of material = 704 cm³

Difference of curved surface areas

2πh(R − r)

Volume of hollow cylinder

πh(R² − r²) = πh(R − r)(R + r)

Internal curved surface area 2πrh

R − r = 2 cm

R + r = 4 cm

Hence R = 3 cm and r = 1 cm

Internal CSA = 2πrh

= 2 × `22/7` × 1 × 28

= 176 cm²