Answer:
The 12'' one.
Explanation:
The crust is at the perimeter of the pizza, and the pizza is a circle, so we just need to calculate the perimeter of the different pizza sizes, and see which one has a perimeter of 37.68 in.
First, you should remember that for a circle of radius R, the perimeter is:
P = 2*3.14*R
(notice that the measures in the image are the diameters of the pizzas, and the radius is half of the diameter)
The radius that we need to have if we want a perimeter of 37.68 in is given by:
P = 37.68 in = 2*3.14*R
(37.68 in)/(2*3.14) = R = 6 inches.
Then we need a pizza of 6 inches (or a diameter of 2*6 inches = 12 inches)
Then the pizza that Ms. Van Rock should get is the 12 inch one.