Geometry and TrigonometryEasy–MediumCircles: area and circumference
Geometry and Trigonometry practice question
A circle has a radius of 6. What is its area? (Use A = πr².)
- A. 12π
- B. 18π
- C. 36πCorrect
- D. 72π
Answer: C. 36π
A = π(6²) = 36π. Choice A (12π) is the circumference formula 2πr — don't mix area and circumference.
Why the other answers are wrong
- A. 12π
- That's the circumference, 2πr = 2π(6) = 12π. Area requires squaring the radius: π(6²) = 36π.
- B. 18π
- No step in A = πr² produces 18π — that's exactly half the correct area. Square the radius first: 6² = 36, so A = 36π.
- D. 72π
- You squared the radius correctly but also multiplied by 2, mixing in the 2 from the circumference formula. Area is just πr² = 36π.
More Geometry and Trigonometry questions
- Easy–Medium
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A circle has a radius of 5. What is its circumference? (Use C = 2πr.) - Easy–Medium
What is the midpoint of the segment joining the points (2, 3) and (8, 11)? - Easy–Medium
What is the measure, in degrees, of angle B? - Easy–Medium
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What is the value of cos A?
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