SOLUTION: If 20 people complete the work in 30 days, then after how many days should 5 people go on leave so that the work is completed in 35 days. answer is 5 days.. but how please

Question 805112: If 20 people complete the work in 30 days, then after how many days should 5 people go on leave so that the work is completed in 35 days.

answer is 5 days..
but how please share the complete methods to solve the question.
thanks
Answer by richwmiller(17219) (Show Source): You can put this solution on YOUR website!
20 people working 30 days are 600 man work days to finish the job.
If it were 5 days it would be
20*5=100 man work days.
15 people working for 30 more days
15 * 30=450 man work days
100+450=550
that only adds up to 550 man work days which isn't enough to finish the job.
The correct answer is
20x+15y=600,
x+y=35
x = 15, y = 20
5 people leave after 15 days
and 15 people finish the work in 20 more days

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