Question 609756
At an aquarium two different pipes can be used to fill one of the large tanks.
 Pipe A can fill the tank in 7 hours. Pipe B can fill tank in 9 hours.
 The aquariums manager would like to fill the tank in less than 4 ours.
 Is it possible to do this by using both pipes at the same time?
:
See how long (t) it would take with both pipes filling the tank
Let the full tank = 1
:
{{{t/7}}} + {{{t/9}}} = 1
multiply by 63, results
9t + 7t = 63
t = {{{63/16}}}
t = 3.9375 hrs. the answer is yes.