Question

 The radius and height of a cylinder are in the ratio of 4 : 7 and its volume is 2816 cm³. Find its radius.
1. 5
2. 6
3. 8
4. 9

Answer 1

Correct Answer - Option 3 : 8

Given:

Ratio of radius and height of cylinder is 4 : 7

Volume of cylinder = 2816 cm³

Concept used:

Mensuration

Calculation:

Let the radius and height of cylinder be 4x and 7x

Volume of cylinder = π r²h

⇒ \(\frac{{22}}{7} × 16{x^2} × 7x = 2816\)

⇒ \({x^3} = \frac{{2816}}{{22\ ×\ 16}}\)

⇒ \({x^3} = \frac{{256}}{{2\; × \;16}} = 8\)

⇒  x = (8)^1/3 = 2

Radius of cylinder = 4x = 4 × 2 = 8cm.