I think i got this one, but am not sure...can you tell me if i am correct???

Bobby bought a pizza and cut it into 12 equal slices (sectors of a circle). He measured the perimeter of a single slice and found it to be 28 inches. What size pizza did he order, that is what is the diameter of the pizza? Nearest tenth of an inch.

2 times the radius plus the arc length is equal to 28 inches

2r + a = 28

the arc length is simply 1/12 * Pie *2r

2r + 1/6 * Pie * r = 28

r = 28/(2 + 1/6pie)

r = 11.1 in

d =22.2 inches

is this right??????????????????????????????????//