Geometry and TrigonometryHardArea of a semicircle from a circumference
Geometry and Trigonometry practice question
A circle has a circumference of 12π. The area of a semicircle of this circle can be written as kπ. What is the value of k?
Answer: 18
2πr = 12π gives r = 6, so the circle's area is 36π and the semicircle's is 18π.
Common wrong answers
- If you answered 6
- 6 is the radius.
- If you answered 36
- 36 is the whole circle.
- If you answered 72
- 72 doubles the circle's area.
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