#### nampe

i have this question, which it reads pretty simple but I am trying to see if someone can walk me through the answer...

A gas cylinder has two vents, V1 and V2, for

discharge. The cylinder empties in 7 minutes when

only vent V1 is open. The cylinder empties in 3

minutes when both vent V1 and vent V2 are open. About

how many minutes will the cylinder take to empty if

only vent V2 is open?

the answer is in actual minutes....

thanks

pedro