Geometry and TrigonometryEasyFormula for circumference
Geometry and Trigonometry practice question
A circle has a radius of 5 centimetres. Which expression gives its circumference, in centimetres?
- A. 10πCorrect
- B. 25π
- C. 5π
- D. 5π²
Answer: A. 10π
Circumference = 2πr = 2π(5) = 10π.
Why the other answers are wrong
- B. 25π
- 25π is the area, πr².
- C. 5π
- 5π forgets the factor 2.
- D. 5π²
- π is not squared.
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