SOLUTION: I following problem has me confused. I came up with the answer 4.5, I don't think it's right. Could I have some assistance in solving it. thank you. One irrigation system needs abo

Algebra ->  Customizable Word Problem Solvers  -> Numbers -> SOLUTION: I following problem has me confused. I came up with the answer 4.5, I don't think it's right. Could I have some assistance in solving it. thank you. One irrigation system needs abo      Log On

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Question 131389: I following problem has me confused. I came up with the answer 4.5, I don't think it's right. Could I have some assistance in solving it. thank you. One irrigation system needs about 3 times as long to complete a job as another irrigation system. When both systems operate at the same time, the job can be completed in 9 hours. How much time is required for the faster system to complete the job by itself?
Answer by TakeATuition.com(57) About Me  (Show Source):
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SOLUTION -

Let the time taken by one irrigation system be x hours
therefore work done in 1 hour = 1/x
and the time taken by another irrigation system be 3x
therefore work done in 1 hour = 1/3x

when both system operates then work done in 9 hours
therefore we have
1/x + 1/3x = 1/9

(3+1)/3x = 1/9

4/3x = 1/9

now by cross multiplication we have

36 = 3x

36/3 = 3x/3

x = 12
therefore faster system required 12 hours to complete the job by itself.
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