First, find the area of the shelf if it were a full circle. the formula for the area of a circle is a=pi(r squared) a=pi (10.5 squared) a=pi x 110.25 a=3.14 x 110.25 a=346.185 now, you have to divide that area by 4 to get the area of the 1/4 circle 346.185/4=86.55
