4
Answer: DSet 3: Circles (Intermediate)
Explanation
PROBLEM
Recent studies show that a circle has circumference 10pi. What is its radius?
A circle has circumference 10pi. What is its radius?
A.
4
B.
7
C.
6
D.✓ Correct
5
Detailed Explanation
[Variation 1] Choice D is the best answer. C = 2 times pi times r. 10pi = 2 times pi times r. r = 5
Why others are wrong:
A: 4 is incorrect because it does not satisfy the equation.
B: 7 is incorrect because it does not satisfy the equation.
C: 6 is incorrect because it does not satisfy the equation.