Question

Together, two pipes can fill a tank in 3 hours.

One pipe alone can fill the tank in 5 hours.
How long does it take for the other pipe to
fill the tank alone?

Answer 1

Answer: 7.5 (h)

Explanation:

Let say

a the outflow of the first pipe

b the outflow of the second pipe

T the volume of the tank.

x the time for filling with the second pipe

two pipes can fill a tank in 3 hours: a*3+b*3=T

One pipe alone can fill the tank in 5 hours : a*5=T

3*b=T -3a ==> 3b= 5a*3a=2a

b=2a/3

b*x=T ==> 2/3*a*x=T ==> 2/3*T/5*x=T ==> 2/15*x=1

x=15/2 = 7.5 (hours)