The radius of a wire is decreased to one-third. If volume remains the same, the length will become

Options

A. 2 times
B. 3 times
C. 6 times
D. 9 times

Answer

D

Explanation

Let the radii be R and `((R)/(3))` and the heights be h and H respectively. Then,
`pi R^(2) h = pi xx ((R)/(3))^(2) xx H rArr H = 9h`