2

Set 4: Circles (Intermediate)

Explanation

Answer: B

PROBLEM

Recent studies show that a circle has area 25pi. What is its radius?

A circle has area 25pi. What is its radius?

A.

6

B.

5

✓ Correct
C.

4

D.

3

Detailed Explanation

[Variation 1] Choice B is the best answer. A = pi times r squared. 25pi = pi times r squared. r squared = 25. r = 5

Why others are wrong:
A: 6 is incorrect because it does not satisfy the equation.
C: 4 is incorrect because it does not satisfy the equation.
D: 3 is incorrect because it does not satisfy the equation.