Question 92008
The plan is to put up a total of 220 yards of fencing.  In the morning 80 yards are erected, 
so the remaining fence to be installed is 220 yards minus the 80 yards or 140 yards left
to go.
.
In the afternoon 40% (or 0.4) of the remaining fence is installed.  Since 140 yards is 
the remaining amount and only 0.4 times that is installed, then 140 * 0.4 = 56 yards is
installed in the afternoon.  That means that on that one day a total of 80 + 56 yards or
136 yards was the amount installed.
.
The percentage of fence installed on that day was 136/220  which is 0.618181 and this converts
to 61.818% which rounds off to 62%.
.
Hope this helps you to understand the problem.