Question 931722
x the time of the Larger hose
{{{1/x + 1/(4x) = 1/20min}}} |Multiplying thru by 20x so as all denominators = 1
20 + 5 = x
25min = x, the time of the Larger hose.  Smaller hose takes 100min {{{4*25}}}
And..checking
1/25 + 1/100 =  4/100 + 1/100 = 5/100 = 1/20