The ratio of the rate of flow of water in pipes varies inversely as the square of the radius of the pipes. What is the ratio of the rates of flow in two pipes diameters 2 cm and 4 cm?

4 : 1

Given: $d_1​=2$ cm

$d_2​=4$ cm

Solution: Since the diameter are 2cm and 4cm.

The replacement ratio of the two pipes are 1cm and 2cm

$r_1​=1$cm

$r_2​=2$cm

Square of the ratio of the pipes are 1 and 4

∴ The ratio of rates of flow in two pipes = $1 : \frac{1}{4}$

$⇒ \frac{4}{1}$