Geometry and TrigonometryEasy–MediumArea of a ring between concentric circles
Geometry and Trigonometry practice question
Two circles share the same centre and have radii 3 and 5. The area of the region between the two circles can be written as kπ. What is the value of k?
Answer: 16
Area = π(5²) − π(3²) = 25π − 9π = 16π, so k = 16.
Common wrong answers
- If you answered 2
- 2 is the difference of the radii.
- If you answered 4
- 4 is (5 − 3)², the square of the difference of the radii, not the difference of the squares.
- If you answered 34
- 34 adds the areas instead of subtracting.
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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