SOLUTION: A sink has two faucets: one for hot water and one for cold water. The sink can be filled by a cold water faucet in 5 minutes. If both faucets are open, the sink is filled in 4 minu

Algebra ->  Rate-of-work-word-problems -> SOLUTION: A sink has two faucets: one for hot water and one for cold water. The sink can be filled by a cold water faucet in 5 minutes. If both faucets are open, the sink is filled in 4 minu      Log On


   

Question 959645: A sink has two faucets: one for hot water and one for cold water. The sink can be filled by a cold water faucet in 5 minutes. If both faucets are open, the sink is filled in 4 minutes. How long does it take to fill the sink with just the hot water faucet open?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Add their rates of filling
Let +t+ = time in minutes to fill
sink with just hot water faucet open
---------------------------------
+1%2F5+%2B+1%2Ft+=+1%2F4+
Multiply both sides by +20t+
+4t+%2B+20+=+5t+
+t+=+20+
With just the hot water faucet open,
the sink fills in 20 min
---------------------
check:
+1%2F5+%2B+1%2Ft+=+1%2F4+
+1%2F5+%2B+1%2F20+=+1%2F4+
+4%2F20+%2B+1%2F20+=+5%2F20+
+5%2F20+=+5%2F20+
OK