Problema Solution
A faucet can fill an empty utility sink 3 minutes. The drain can empty a full sink in 5 minutes. If by mistake both are open , how long will it take to fill an empty sink?
Answer provided by our tutors
We consider the volume of the silk is V ,then the flow of fill is V/3,and the flow of drain is V/5, if they are both open ,the total flow is V/3-V/5, and equals 2V/15, so the time to fill the silk is V/(2V/15),equals 15/2 min, also 7.5 min.