Question

A cylinder has a diameter of 20 cm. The area of the curved surface is 100 cm² (sq. cm). Find:

1. the height of the cylinder correct to one decimal place. 
2. the volume of the cylinder correct to one decimal place.

Answer 1

Diameter of the cylinder = 20 cm 

Hence, Radius (r) = 10 cm 

Height = h cm 

(i) Curved surface area = 2πrh 

∴ 2πrh = 100 cm²

`=> 2 xx 22/7 xx 10 xx h = 100`

`=> h = (100 xx 7)/(22 xx 10 xx 2)`

= `35/22`

`=>` h = 1.6 cm

(ii) Volume of the cylinder = πr²h

= `22/7 xx 10 xx 10 xx 1.6`

= `(22 xx 100 xx 1.6)/7`

= 502.857 cm³

= 502.9 cm³

or 

= `22/7 xx 10 xx 10 xx 35/22`

= 500 cm³