Word problem: Pumps A, B, C working at respective rates....

mcheytan

Junior Member
Joined
Jan 25, 2008
Messages
51
I have a problem that I have solved but I don't get the correct answer.

Pumps A, B, C are working at their respective rates. Working together, pumps A and B fill a tank in 6/5 hours; pumps A and C fill it for 3/2 hours, and pumps B and C fill it for 2 hours. How much time they need to fill the tank if all working together at their respective rates???

Set up:
1/A + 1/B =5/6 h
1/A + 1/C = 2/3 h
1/B + 1/C=2h

I solve for A and then solve for C and then substitute in the last equation. I find that :
1/B=17/20h
1/C=23/20h
1/A=7/20h

I add them up together and find that T=47/20h=2h and 35 min....
However the answer I should be 1h.

Can you guys tell me what I am doing wrong???
Thanks
Mira
 
Re: Word problem

In your original 3 equations the first 2 are correct but the right side of 3rd should be 1/2.
 
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