### Home > CC2 > Chapter 9 > Lesson 9.1.1 > Problem 9-10

Estimate the circumference or diameter for each of the following circles. For each one, give your reasoning.

The diameter is

cm. What is the circumference? The circumference of a circle can be thought of as the length of a string that wraps exactly around it once.

You can calculate the circumference by multiplying the diameter by, which is just over . The circumference is

cm, or just over cm. The diameter is

meters. What is the circumference? What length is just over

times longer than meters? The circumference is

mile. What is the diameter? Since the circumference is just over

times the diameter, it makes sense that the diameter is about one third the length of the circumference. The circumference is

inches. What is the diameter? Using the same hint as in part (c), approximate your answer by substituting

for once again. The diameter is approximately

inches.