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A certain tank has an inlet valve and an outlet valve.
The tank can be filled via the inlet valve in 6 minutes and emptied (from full) via the outlet valve in 10 minutes.
If both valves are operating, how long would it take to fill the tank if it was empty to begin with?
Let t = time required to fill the tank when both valves are on
Let the completed job (a full tank) = 1
+ means fill (inlet), - means drain (outlet)
Multiply equation by 30 to get rid of the denominators, results:
5t - 3t = 30
2t = 30
t = 15 min to fill with both open
Check on calc:
2,5 - 1.5 = 1