SOLUTION: A pool can be filled in 12 hours using pipe A, or in 30 hours using pipe B. If both pipes are used, how long it will take to fill the pool?

Algebra ->  Rate-of-work-word-problems -> SOLUTION: A pool can be filled in 12 hours using pipe A, or in 30 hours using pipe B. If both pipes are used, how long it will take to fill the pool?      Log On


   



Question 548634: A pool can be filled in 12 hours using pipe A, or in 30 hours using pipe B. If both pipes are used, how long it will take to fill the pool?
Answer by Earlsdon(6294) About Me  (Show Source):
You can put this solution on YOUR website!
Let x = the number of hours to fill the pool.
The rate of filling for pipe A is x%2F12 and for pipe B is x%2F30
The rate of filling for both A and B is:
x%2F12%2Bx%2F30+=+7x%2F60 so to fill the pool, set this equal to 1 and solve for x:
7x%2F60+=+1 Multiply both sides by the multiplicative inverse of 7%2F60 which is60%2F7 to get:
x+=+60%2F7hours or
x+=+8hours and 34.3minutes.