Question 670509
One pipe takes 10 hour to fill 540 gal
so in 1 hour it can fill 54 gal
second pipe can fill in 12 hours

so it can fill 540/12 = 45 gal/hour

Together they fill 54+45 = 99 gal/hour

tank = 540 gal

so they will take 540/99 = 5.44  hours