Question 535024
there were 4 workers that built A WALL IN 5 DAYS 
Find how many man-days to complete wall: 
4 * 5 = 20 man-days
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"THERE 10 WORKERS  HOW MANY DAYS DID IT TAKE THEM TO BUILd A WALL?
let d = no. of days for 10 guys to do it
10d = 20
d = 2 days for 10 guys to do it
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This is in theory only, usually when you get that many together, at least two of them are goof-offs. If they are city workers, the no. of goof-offs will quadruple.
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However, your teacher probably is not interested in the social aspect of the situation, have a Blessed Thanksgiving! C