SOLUTION: two pipes p and q can fill a tank 12 and 15 minutes respectfully. if both are opened together and at the end 3 minutes. first is closed. how much longer will the tank takes to fill

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Question 741919: two pipes p and q can fill a tank 12 and 15 minutes respectfully. if both are opened together and at the end 3 minutes. first is closed. how much longer will the tank takes to fill
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
two pipes p and q can fill a tank 12 and 15 minutes respectfully.
if both are opened together, and at the end 3 minutes, the first is closed.
how much longer will the tank take to fill?
:
Let t = additional time required to fill the tank
let the completed job = 1; (a full tank)
:
A shared work equation
:
3%2F12 + %28%28t%2B3%29%29%2F15 = 1
multiply by 60 to clear the denominators
60*3%2F12 + 60*%28%28t%2B3%29%29%2F15 = 60*1
cancel the denominators and you have
5(3) + 4(t+3) = 60
15 + 4t + 12 = 60
4t = 60 - 27
4t = 33
t = 33/4
t = 8.25 additional minutes
:
:
See if this check out (the 2nd pipe runs a total of 11.25 min)
3%2F12 + 11.25%2F15 =
.25 + .75 = 1; confirms our solution of t=8.25