SOLUTION: Mary works 2.5 times faster than peter.together,they do a job in 12.5 hours.how long does it take mary working alone to do the same job?

Question 850682: Mary works 2.5 times faster than peter.together,they do a job in 12.5 hours.how long does it take mary working alone to do the same job?
Answer by lwsshak3(11628) (Show Source): You can put this solution on YOUR website!
Mary works 2.5 times faster than peter.together,they do a job in 12.5 hours.how long does it take mary working alone to do the same job?
***
let x=time it takes peter to finish the job working alone
1/x=his work rate
2.5/x=mary's work rate
1/12.5=work rate peter and mary working together to finish the job
..
sum of indv. work rates=work rate working together

3.5/x=1/12.5
x=43.75
hours it takes mary working alone to do the same job=43.75/2.5=17.5

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