1
Answer: DSet 2: Circles (Intermediate)
Explanation
PROBLEM
A circle has area 81pi. What is its radius?
A circle has area 81pi. What is its radius?
A.
10
B.
7
C.
11
D.✓ Correct
9
Detailed Explanation
Choice D is the best answer. A = pi times r squared. 81pi = pi times r squared. r squared = 81. r = 9
Why others are wrong:
A: 10 is incorrect because it does not satisfy the equation.
B: 7 is incorrect because it does not satisfy the equation.
C: 11 is incorrect because it does not satisfy the equation.