SOLUTION: one pump can drain a pool in 7 minutes. When a second pump is also used together with the first, the pool only takes 3 minutes to drain. How long would it take the second pump to d

Algebra ->  Rate-of-work-word-problems -> SOLUTION: one pump can drain a pool in 7 minutes. When a second pump is also used together with the first, the pool only takes 3 minutes to drain. How long would it take the second pump to d      Log On


   



Question 746009: one pump can drain a pool in 7 minutes. When a second pump is also used together with the first, the pool only takes 3 minutes to drain. How long would it take the second pump to drain the pool if it were the only pump in use?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Add their rates of draining to get their
rate of draining together
( 1 pool / 7 min ) + ( 1 pool / t min ) = ( 1 pool / 3 )
Solve for +t+
+1%2F7+%2B+1%2Ft+=+1%2F3+
Multiply both sides by +21t+
+3t+%2B+21+=+7t+
+4t+=+21+
+t+=+5.25+
+.25%2A60+=+15+
It will take the 2nd pump
5 min and 15 sec by itself