Hi,
Let x represent the time it takes for the smaller pipe to fill the tank
then (x-5) would be the time for the larger pipe
Question states: Per hr being the equalizer
1/x + 1/(x-5) = 1/6hr
Multiplying each term on both sides of the equation by 6x(x-5) so as all denominators = 1
6(x-5) + 6x = x(x-5)
6x - 30 +6x = x^2 -5x
x^2 -17x +30 = 0
factoring
(x -15)(x-2) = 0
(x-2) = 0 x = 2 (cannot use)
(x -15)= 0 x = 15hr , the time it takes for the smaller pipe to fill the tank
the time would it take the larger pipe to fill it, is 10hr. (15-5)
checking our answer
1/15 + 1/10 = 2/30 + 3/30 = 5/30 = 1/6