SOLUTION: A certain number of men can complete a job in 10 days. if 10 man are absent, the remaining men can do the job in 12 days.how many men were there originaly?

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Question 942172: A certain number of men can complete a job in 10 days. if 10 man are absent, the remaining men can do the job in 12 days.how many men were there originaly?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +n+ = the original number of men
1 man can complete the job in +10n+ days
His rate is +1%2F%2810n%29+ , or ( 1 job ) / ( 10n days )
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If +n+-+10+ men can do the job in 12 days,
then 1 man can do the job in +12%2A%28+n-10+%29+
days
Each man's rate is: +1%2F%28+12%2A%28+n-10+%29%29+
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Each man's rate didn't change, so
+1%2F%28+10n+%29+=+1%2F%28+12%2A%28+n-10+%29%29+
+10n+=+12n+-+120+
+2n+=+120+
+n+=+60+
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there were 60 men originally
check:
60 men can do a job in 10 days
1 man can do the job in 600 days
His rate is +1%2F600+
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+60+-+10+=+50+ men can do the job in 12 days
1 man can do the job in +50%2A12+=+600+ days
His rate is +1%2F600+
OK