SOLUTION: Maria does certain job in 5 hours. Her friend does the same job in x hours. If both of them work together the work gets completed in 3 hrs.

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Question 332707: Maria does certain job in 5 hours. Her friend does the same job in x hours. If both of them work together the work gets completed in 3 hrs.
Answer by mananth(16946) About Me  (Show Source):
You can put this solution on YOUR website!
Maria does the job in 5 hours
so she does 1/5 of the job in 1 hour
..
friend does the job in x hours
so she does 1/x of the job in 1 hour
..
together they do (1/x)+(1/5) of the job in 1 hour.
= LCM = 5x
(5+x)/5x of the job they do in 1 hour
so they take 5x /( x+5) hours to do the job together.
which is = 3hours
..
5x/(x+5)=3
5x=3(x+5)
5x=3x+15
5x-3x=15
2x=15
x= 15/2 = 7.5 hours
The time taken by friend to do it alone
..
CHECK
2/15 + 1/5 = (2+3) / 15
= 5/15
= 1/3 of the job
so they take 3 hours together