Question 956640
To do 1 job takes {{{ 9*28 = 252 }}} man-days
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(a)
I can say:
1 job takes {{{ 14*d = 252 }}} man-days
{{{ d = 252/14 }}}
{{{ d = 18 }}}
14 men will take 18 days
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(b)
1 job takes {{{ m*56 = 252 }}}
{{{ m = 252/56 }}}
{{{ m = 4.5 }}}
4.5 men will take 56 days
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You can do this another way:
9 men do a piece of work in 28 days.
1/3 as many men takes 3 times as long, so
3 men take 84 days
7 times as many men take 1/7 times as long, so
21 men take 12 days
twice as many men take 1/2 this time, so
42 men take 6 days
1/3 as many men take 3 times as long, so
14 men take 18 days to do the job
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This is just an example of what you might do