SOLUTION: One pipe can fill a swimming pool in 6 hours, and another pipe can do it in 9 hr. How long will it take the two pipes working together to fill the pool 3/4 full?

Algebra ->  Rate-of-work-word-problems -> SOLUTION: One pipe can fill a swimming pool in 6 hours, and another pipe can do it in 9 hr. How long will it take the two pipes working together to fill the pool 3/4 full?      Log On


   

Question 409722: One pipe can fill a swimming pool in 6 hours, and another pipe can do it in 9 hr. How long will it take the two pipes working together to fill the pool 3/4 full?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let t = time for both pipes to fill 3/4 of the pool
given:
R%5B1%5D+=+1%2F6 1 pool/6 hours
R%5B2%5D+=+1%2F9 1 pool/9 hours
---------------------
R%5B1%5D+%2B+R%5B2%5D+=+%283%2F4%29%2Ft
1%2F6+%2B+1%2F9+=+%283%2F4%29%2Ft
Multiply both sides by 18t
3t+%2B+2t+=+%283%2A18%29%2F4
5t+=+27%2F2
t+=+2.7 hr
The 2 pipes together take 2.7 hr, or 2 hrs and 42 min
to fill 3/4 of the pool