Set 5: Circles (Intermediate)

[Variation 1] **Choice A is the best answer.** C = 2 times pi times r. 18pi = 2 times pi times r. r = 9

Explanation

Answer: A

PROBLEM

Recent studies show that a circle has circumference 18pi. What is its radius?

A circle has circumference 18pi. What is its radius?

✓ Correct

Detailed Explanation

[Variation 1] Choice A is the best answer. C = 2 times pi times r. 18pi = 2 times pi times r. r = 9

Why others are wrong:

B: 7 is incorrect because it does not satisfy the equation.

C: 8 is incorrect because it does not satisfy the equation.

D: 10 is incorrect because it does not satisfy the equation.