Question 60890
One approach to this kind of problem is to first calculate the rate that each pipe can fill the tank.
If it takes pipe A 8 minutes to fill the tank, then pipe A can fill 1/8 of the tank in 1 minute.
If it takes pipe B 12 minutes to fill the tank, then pipe B can fill 1/12 of the tank in 1 minute.
Working together, pipe A and pipe B can fill (1/8 + 1/12) of the tank in 1 minute.
1/8 + 1/12 = (3+2)/24 = 5/24 of the tank in 1 minute.
5/24 of tank = 1 min. Multiply both sides by the reciprocal (24/5)
1 = 24/5 mins. = 4.8 mins.
The tank can be filled in 4.8 minutes by both pipes working together.