SOLUTION: a contractor estimated that 20 men can complete a tank in 10 days. After working for three days 5 men went to home and not come back to work again, so in how many days they will co

Question 667151: a contractor estimated that 20 men can complete a tank in 10 days. After working for three days 5 men went to home and not come back to work again, so in how many days they will complete the remaining work?
Answer by vleith(2983) (Show Source): You can put this solution on YOUR website!
If 20 men can do a job in 10 days, what is total work for that project in mendays?

You are told that for the first 3 days all 20 men were working? How much work did they do?

So how much work is left after 3 days?

From the 4th day on, the project has only 15 men working on it?
So how many days must 15 men work in order to produce 140mandays of work?

The remaining 15 men must work 9 1/3 days to finish the job.
Notice how the units (men and days in this problem) are variable that can divide and multiply just like any other variable. As you move on in higher math (and into using math in physics etc) make sure to use units to help you make solve problems like this. If the units don't 'make sense' in a solution, then it is possible the solution you have may be in error.
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