Length of the radius of the small pizza = 15 inches
Circumference of the small pizza :



Thus, the circumference of the small pizza = 94.2 inches
Length of the radius of the large pizza = 24 inches
Circumference of the large pizza :



Thus, the circumference of the large pizza = 150.72 inches
Ratio of the circumferences of the two pizzas :



Let us simplify the fraction :





Thus, the ratio of their circumferences = 5:8
Therefore, the ratio of the circumferences of the pizzas as a fraction 