Seth wants to create a replica of a doughnut for a rooftop sign for his bakery. The replica has a diameter of 18 feet. The diameter of the hole in the center is equal to the replica's radius.

Question

Seth wants to create a replica of a doughnut for a rooftop sign for his bakery. The replica has a diameter of 18 feet. The diameter of the hole in the center is equal to the replica's radius.

Once the replica is built, Seth wants to string small lights around the outer edge. How long will the string of lights need to be?

A. Write a numerical expression for the length of the string of lights needed.

B. Simplify your expression. Use 3.14 as an approximation for .

C. Explain how you got your answer.

Answer 1

C = 2Πr

d = 18

d = 2r

r = 9

C = 2Π9

C = (2)(3.14)(9)

C = 56.52 feet

This is the length of the string of lights.