<PRE><B>Question 652081</B>
OK.  It takes 2*3.5 or 7 mason hours to build the wall. In other words, one mason can build the wall in 7 hours; two masons can build the wall in 7/2=3.5 hours; 3 masons can build the wall in 7/3 hours, etc.

5 masons can build the wall in 7/5=1.4 hours

Another way to look at this problem:
Let x=amount of time it takes 5 masons to build the wall
Then 5 masons work at the rate of 1/x wall per hour
One mason works at the rate of 1/5x wall per hour
But 2 masons work at the rate of 1/3.5 wall per hour
And one mason works at the rate of 1/7 wall per 
soooo:
1/5x=1/7
5x=7
x=1.4 hours----time it takes 5 masons to build the wall

Hope this helps---ptaylor
</PRE>