Question 353480
This is all good:
A= 10 x 25 =250 A of circle 3.14 x 5^2 = 78.54 
.
However, since the sprinkler is placed on a corner, only 1/4 of the water will hit the lawn -- therefore:
area covered by sprinkler is 78.54(.25) = 19.63
.
Percent coverage:
19.63/250 = .079 or 7.9%