A circle has radius 5. What is its circumference? Use π ≈ 3.14.

A circle has radius 5. What is its circumference? Use π ≈ 3.14.

• A. 25.0
• B. 15.7
• C. 31.4
• D. 20.0

Answer: (C)

The main idea is the circumference is 2π times the radius. With radius 5 and π approximated as 3.14, compute 2 × 3.14 × 5 = 31.4. So the circumference is 31.4 units. This value arises directly from the formula C = 2πr. The other numbers don’t match this calculation with r = 5, for example 15.7 would come from πr if you forgot the factor of 2, while the remaining values don’t align with the standard circumference formula using r = 5.

The main idea is the circumference is 2π times the radius. With radius 5 and π approximated as 3.14, compute 2 × 3.14 × 5 = 31.4. So the circumference is 31.4 units. This value arises directly from the formula C = 2πr. The other numbers don’t match this calculation with r = 5, for example 15.7 would come from πr if you forgot the factor of 2, while the remaining values don’t align with the standard circumference formula using r = 5.