Set 5: Circles (Beginner)

[Variation 1] **Choice D is the best answer.** Area = pi times r squared = pi times 9 squared = 81pi

Explanation

Answer: D

PROBLEM

Recent studies show that a circle has radius 9. What is its area? (Express answer as a number times pi)

A circle has radius 9. What is its area? (Express answer as a number times pi)

90pi

18pi

9pi

81pi

✓ Correct

Detailed Explanation

[Variation 1] Choice D is the best answer. Area = pi times r squared = pi times 9 squared = 81pi

Why others are wrong:

A: 90pi is incorrect because it does not satisfy the equation.

B: 18pi is incorrect because it does not satisfy the equation.

C: 9pi is incorrect because it does not satisfy the equation.