Question 1108786
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... After 20 days 10 men complete 1/3 work.
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r, one-man rate
Amount of job done was {{{1/3}}};


{{{10*r*20=1/3}}}


{{{r=1/(3*10*20)}}}


{{{highlight_green(r=1/600)}}}



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contract to build a house in 30 days;
how many men required to complete full work?
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Need to do still, {{{2/3}}} of the job, and use additional n men with the same 10, and need to do this amount of work in 10 days.


{{{(n+10)r*10=2/3}}}

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{{{(n+10)(1/600)*10=2/3}}}

{{{n+10=(2/3)(600/10)}}}

{{{n+10=(2/3)60}}}

{{{n+10=2*20}}}

{{{n=40-10}}}

{{{highlight(n=30)}}}------------30 more men needed, to complete the work.