Question 1092198
<br>I personally nearly always find it easiest to work problems like this by looking at how the number of feet of pipe is affected by the change in each of the other parameters in the problem.<br>
30 men instead of 24: an increase by a factor of 30/24, or 5/4.
18 days instead of 20: a decrease by a factor of 18/20, or 9/10.<br>
Applying these factors to the given number of 400 feet of pipe, the new number of feet of pipe is<br>
{{{400(5/4)(9/10) = 500(9/10) = 450}}}<br>