Question 323118
A large pipe and a smaller pipe are connected to a tank. The large pipe can empty the tank in nine minutes. The small pipe can empty the tank in seventeen minutes. If both pipes are used at the same time, how long will it take to empty the tank?
---------------------
The large pipe empties 1/9 of the tank per minute.
The small one does 1/17 per minute.
Together, they do 1/9 + 1/17 per minute, = 26/153 tanks/minute
--> 153/26 minutes/tank
=~ 5.885 minutes
-------------------
Use the shortcut, product/sum
--> 9*17/(9+17)
= 153/26 minutes