Tap A takes 6 minutes to fill a tank
So A's filling rate = 1 tankful per 6 minutes or 1/6 of a tankful per minute.
and Tap B takes 9 minutes to fill the same tank.
So B's filling rate = 1 tankful per 9 minutes or 1/9 of a tankful per minute.
Pipe C can empty the tank in 15 minutes.
So C's 'emptying' rate = 1 tankful per 15 minutes or 1/15 of a tankful per minute.
But that's to be interpreted as a negative filling rate.
C's "filling" rate = -1 tankful per 15 minutes or -1/15 of a tankful per minute.
How long will it take to fill up the tank if the pipe is
in use when both taps are turned on?
Both taps? But there are three pipes mentioned. Did you
mean all three pipes were turned on, or just A and B?
If you like, you can tell me what you meant in the thank-you
note form below, and I'll get back to you by email.
Edwin
