Question 418676
one pipe fills a tank in 8 minutes, another pipe can fill it in 12 minutes. find the time taken to fill the tank when both pipes are running together?

. 
Let x = time (minutes) it takes for both
then
x(1/8 + 1/12) = 1
multiplying both sides by 24:
x(3 + 2) = 24
5x = 24
x = 24/5
x = 4.8 minutes