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- Use your formula to find the circumference of a circle with a diameter of 24.5 cm. Give your answer to the nearest tenth of a centimeter.
- Use your formula to find the diameter of a circle with a circumference of 48 cm. Give your answer to the nearest tenth of a centimeter.
Check-In: Questions 20–26
There is a definite relationship between the circumference and the diameter of a circle.
- The circumference of a circle is equal to the diameter of the same circle times
. This means that C = D. - The diameter of a circle is equal to the circumference of the same circle divided by . This means that D = C ÷ .
Find the circumference or the diameter of a circle to solve the following problems. Use the 
key on your calculator.
- Nila measured the circumference of a circle as 9
inches. Find the diameter. Round your answer to the nearest inch. - Brandon measured the diameter of a circle as 87 cm. Find the circumference. Round your answer to the nearest tenth of a centimeter.
- Copy the table at the right. Then find the missing values of D (diameter) and C (circumference). Round answers to the nearest tenth of a centimeter.
- A tire on a car has an inside diameter of 43 centimeters and an outside diameter of 71 centimeters.
- What is the inner circumference?
- What is the outer circumference?
- How far will the tire roll in one turn?
