Question

A rectangular strip 25 cm × 7 cm is rotated about the long side. Find The total surface area of the solid thus generated.

Answer 1

We have,

Dimension of rectangular strip = 25 cm × 7 cm

When this strip is rotated about its longer side,

The height of the cylinder becomes = 25 cm

Radius = 7 cm

∴ The total surface area of the cylinder = 2πr(h +  r)

= `2 xx 22/7 xx 7(25 + 7)`

= `2 xx 22/7 xx 7 xx 32`

= 1408 cm²