SOLUTION: i dont know how to slove these problems i have the question set up and the answer but i dont know how to solve it together two pipes can fill a vat in 8 hours 24 minutes. if the s

Algebra ->  Rate-of-work-word-problems -> SOLUTION: i dont know how to slove these problems i have the question set up and the answer but i dont know how to solve it together two pipes can fill a vat in 8 hours 24 minutes. if the s      Log On


   

Question 872063: i dont know how to slove these problems i have the question set up and the answer but i dont know how to solve it together two pipes can fill a vat in 8 hours 24 minutes. if the smaller pipe takes 28 hours to fill the vat how long does it take to fill the vat? please help
Found 2 solutions by josgarithmetic, richwmiller:
Answer by josgarithmetic(39628) About Me  (Show Source):
You can put this solution on YOUR website!
The job is, "fill a vat".
R for rate
T for time
J for job or jobs
RT=J

Small and Big pipes together, rate is %281%2F%288%2624%2F60%29%29
Small pipe, rate is 1%2F28
Big pipe, 1%2Ft

Combined rate of both pipes is the sum of the rates of the small pipe and big pipe:
1%2Ft%2B1%2F28=1%2F%288%2624%2F60%29.



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1%2Ft%2B1%2F28=1%2F%28%28460%2B24%29%2F60%29
1%2Ft%2B1%2F28=60%2F%28484%29
1%2Ft%2B1%2F28=15%2F121
1%2Ft=15%2F121-1%2F28
1%2Ft=120%2F28
1%2Ft=30%2F7
t=7%2F30 OR t=14%2F60 hours, meaning 14 minutes

Answer by richwmiller(17219) About Me  (Show Source):
You can put this solution on YOUR website!
The other tutor made several arithmetic errors.
8 24/60= 8.4=84/10
1/t+1/28=5/42
1/t=5/42-1/28
1/t=(140-42)/1176
1/t=98/1176
1/t=1/12
t=12 hours