Question 652094
A stream with a velocity of 1/4 mile per hour can move coarse sand particles
 about 0.02 inch in diameter. 
Approximate the velocity required to carry particles 0.12 inch in diameter.
 Use the fact that the diameter of the largest particle that can be moved by a
 stream varies approximately directly as the square of the velocity of the stream. 
:
let v = velocity of the stream; change 1/4 to .25
:
Write a proportion equation
{{{v^2/.25^2}}} = {{{.12/.02}}}
{{{v^2/.0625}}} = 6
v = {{{sqrt(.0625*6)}}}
v = .612 mph