SOLUTION: 3 pipes fill a tank in 0.375 hours. If 2 of them take 1.25 hours and 10/7 hours respectively to fill it alone, how many hours will the 3rd pipe take to fill it alone?

Algebra ->  Rate-of-work-word-problems -> SOLUTION: 3 pipes fill a tank in 0.375 hours. If 2 of them take 1.25 hours and 10/7 hours respectively to fill it alone, how many hours will the 3rd pipe take to fill it alone?      Log On


   



Question 992309: 3 pipes fill a tank in 0.375 hours. If 2 of them take 1.25 hours and 10/7 hours respectively to fill it alone, how many hours will the 3rd pipe take to fill it alone?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Add their rates of filling to get their
rate filling together
1st pipe's rate:
[ 1 tank filled ] / [ 1.25 hrs ]
2nd pipe's rate:
[ 1 tank filled ] / [ 10/7 hrs ]
3rd pipe's rate:
[ 1 tank filled ] / [ t hrs ]
All 3 pipes together:
[ 1 tank filled ] / [ .375 hrs ]
-------------------------
+1.25+=+5%2F4+
+.375+=+3%2F8+
+1%2F%28+5%2F4%29+%2B+1%2F%2810%2F7%29+%2B+1%2Ft+=+1%2F%283%2F8%29+
+4%2F5+%2B+7%2F10+%2B+1%2Ft+=+8%2F3+
Multiply both sides by +30t+
+24t+%2B+21t+%2B+30+=+80t+
+35t+=+30+
+7t+=+6+
+t+=+6%2F7+ hrs
The 3rd pipe will take 6/7 hrs to fill
the tank working alone
---------------------
check:
+4%2F5+%2B+7%2F10+%2B+1%2Ft+=+8%2F3+
+4%2F5+%2B+7%2F10+%2B+7%2F6+=+8%2F3+
Multiply both sides by +30+
+24+%2B+21+%2B+35+=+80+
+80+=+80+
OK