Question 1027713
<pre>
The other tutor's answer is very wrong.
</pre>
Three workers can do a job in 28 hours. How many more workers 
are needed to do this job in 12 hours?
<pre>
The fewer workers there are the more the hours that are required, 
and the more workers there are, the fewer hours that are required.

Therefore workers and hours are inversely proportional.

The word "inversely" is a form of the word "invert".
So we invert one of the fractions in the proportion. It doesn't
matter which one we invert.

{{{matrix(1,3,

matrix(1,3, workers,1st,time)/matrix(1,3, workers,2nd,time),""="", matrix(1,3, hours,2nd,time)/matrix(1,3,hours,1st,time))}}}

{{{matrix(1,3,

3/x,""="",12/28)}}}

{{{matrix(1,3,

12x,""="",84)}}}

{{{matrix(1,3,

x,""="",7)}}}

7 workers are required, so we need 7-3 or 4 more workers.  

Edwin</pre>