Question 1112556
The contractor figures that:
For {{{ 140 }}} men, their rate of working would be:
{{{ (1/4) / 200 = 1/800 }}} jobs/days
One man would work {{{ 140 }}} times slower than this, or
{{{ 1/112000 }}} jobs/days
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In {{{ 60 }}} days, the {{{ 140 }}} men completed:
{{{ ( 1/800 )*60 = 3/40 }}} of the job, so
there is {{{ 37/40 }}} left to do in {{{ 200 - 60 = 140 }}} days
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Let {{{ x }}} = number of men needed to finish 
the job in {{{ 140 }}} days
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{{{ x*( 1/112000 ) = (( 37/40 )) / 140 }}}
{{{ x = ( 37*112000 ) / ( 40*140 ) }}}
{{{ x = 4144000 / 5600 }}}
{{{ x = 740 }}}
{{{ 740 - 140 = 600 }}}
He needs to hire 600 more men to finish on time
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Definitely get a 2nd opinion on this if you have the
time. If you know what the answer should be, don't bother