Geometry and TrigonometryEasy–MediumCircumference of a circle
Geometry and Trigonometry practice question
What is the circumference of a circle with radius 7?
- A. 14πCorrect
- B. 7π
- C. 49π
- D. 28π
Answer: A. 14π
Circumference is 2πr. With r = 7, that's 2π(7) = 14π.
Why the other answers are wrong
- B. 7π
- 7π is πr, missing the factor of 2. Circumference uses the diameter, which is 2r = 14.
- C. 49π
- 49π is the AREA, πr². Circumference is a length, 2πr.
- D. 28π
- 28π doubles the diameter. The diameter is already 2r = 14; circumference is π times the diameter, 14π.
More Geometry and Trigonometry questions
- Easy–Medium
A circle has a radius of 6. What is its area? (Use A = πr².) - Easy–Medium
A right triangle has legs of length 6 and 8. What is the length of the hypotenuse? - Easy–Medium
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
What is the area, in square centimeters, of the trapezoid?
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