Question 1031233
An old water pipe is to be replaced by a new one so that twice as much water can flow through the pipe.
 What is the ratio of the radius of the new pipe to that of the old pipe?
:
To make twice as much water flow thru the pipe, the cross section area has to be doubled
:
Let R = the radius of the larger pipe
Let r = the radius of the smaller
:
{{{(pi*R^2)/(pi*r^2)}}} = {{{2/1}}} 
Cancel pi
{{{(R^2)/(r^2)}}} = {{{2/1}}}
{{{R/r}}} = {{{sqrt(2/1)}}}
{{{R/r}}} = {{{1.414/1}}} is the ratio of radius the new pipe to the radius of the old pipe