Question 885169
A job can be done by 25 men in 32 days. After 8 days, 5 men left. how long will it take the remaining men to finish the job?
<pre>
1 job can be done by 25 men in 32 days.

So when they had worked 8 days, they had done {{{1/4}}}th of the job, since 8 is
{{{1/4}}}th of 32.

So that left {{{3/4}}} of the job for the 20 to do.

Also since a job can be done by 25 men in 32 days,

then 1 man would take 25 times as long or 800 days.

So each man's work rate is {{{matrix(1,2,1,job)/matrix(1,2,800,days)}}} or
{{{matrix(1,2,1/800,job/day)}}}

20 men's work rate is 20 times the work rate of one man or 20 times
{{{matrix(1,2,1/800,job/day)}}} or {{{matrix(1,2,20/800,job/day)}}} which reduces to {{{matrix(1,2,1/40,job/day)}}} 

Suppose it took them N days to finish the job. Then 

{{{matrix(1,2,1/40,job/day)}}}{{{"×"}}}{{{matrix(1,2,N,days)}}} {{{""=""}}}{{{matrix(1,2,3/4,job)}}}

{{{expr(1/40)N}}}{{{""=""}}}{{{3/4}}}

Multiply both sides by 40

10N = 30
  N = 3

It would take them 3 days.

Edwin</pre>