4

Set 5: Circles (Intermediate)

Explanation

Answer: C

PROBLEM

Intriguingly, a circle has area 49pi. What is its radius?

A circle has area 49pi. What is its radius?

A.

8

B.

9

C.

7

✓ Correct
D.

6

Detailed Explanation

[Variation 2] Choice C is the best answer. A = pi times r squared. 49pi = pi times r squared. r squared = 49. r = 7

Why others are wrong:
A: 8 is incorrect because it does not satisfy the equation.
B: 9 is incorrect because it does not satisfy the equation.
D: 6 is incorrect because it does not satisfy the equation.