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Advanced MathEasyCoefficient of pi in a circle area

Advanced Math practice question

The area of a circle with radius r is πr². When r = 3, the area can be written as kπ. What is the value of k?

Answer: 9

π(3)² = 9π, so k = 9.

Common wrong answers

If you answered 3
3 is r, not r².
If you answered 6
6 is 2 × 3, using 2r instead of r².
If you answered 28
28 rounds 9π itself; the question asks for the coefficient of π.

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