SOLUTION: Pipe A takes 20min to fill tank while pipe B Takes 30 min and pipe C Takes 40 min to empty it.if the all pipes work together...how many time it will take to fill tank..??? Pleas

Algebra ->  Rate-of-work-word-problems -> SOLUTION: Pipe A takes 20min to fill tank while pipe B Takes 30 min and pipe C Takes 40 min to empty it.if the all pipes work together...how many time it will take to fill tank..??? Pleas      Log On


   

Question 828258: Pipe A takes 20min to fill tank while pipe B Takes 30 min and pipe C Takes 40 min to empty it.if the all pipes work together...how many time it will take to fill tank..???
Please elaborate the answer
Answer by Seutip(231) About Me  (Show Source):
You can put this solution on YOUR website!
Step 1: Assign variables:
Let x = time taken to fill up the tank
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Step 2: Use the formula:
1/40 is negative since it is draining not fulling it. :)
1%2F20%2B1%2F30-1%2F40=1%2Fx
120%281%2F20%2B1%2F30-1%2F40%29=%281%2Fx%29120 Multiply both sides by 120 since it is the LCM of 20, 30 AND 40 :)
6%2B4-3=120%2Fx
7=120%2Fx
X=120%2F7
It would take 120/7 minutes to full the tank :)
HOPE that helps O:)