Worked example
A circle has radius 2 cm. What is its exact area in square centimeters, written as a multiple of π?
Answer & why
Answer: 4π
Area = πr2 = π × 22 = 4π square centimeters.
Grade 10 · Math
Find a circle’s exact area
Use radius squared to express an exact circle area in terms of π.
8 authored questions + worked example
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All questions
All 8 authored questions for this skill.
Question 1
A circle has radius 8 cm. What is its exact area in square centimeters, written as a multiple of π?
- 64π
- 66π
- 16π
- 256π
A hint
Use the radius, not the diameter, in πr2.
Answer & why
Answer: 64π
Area = πr2 = π × 82 = 64π square centimeters.
Question 2
A circle has radius 9 cm. What is its exact area in square centimeters, written as a multiple of π?
- 81π
- 324π
- 18π
- 83π
A hint
Use the radius, not the diameter, in πr2.
Answer & why
Answer: 81π
Area = πr2 = π × 92 = 81π square centimeters.
Question 3
A circle has radius 2 cm. What is its exact area in square centimeters, written as a multiple of π?
- 4π
- 5π
- 16π
- 6π
A hint
Use the radius, not the diameter, in πr2.
Answer & why
Answer: 4π
Area = πr2 = π × 22 = 4π square centimeters.
Question 4
A circle has radius 3 cm. What is its exact area in square centimeters, written as a multiple of π?
- 6π
- 11π
- 9π
- 36π
A hint
Use the radius, not the diameter, in πr2.
Answer & why
Answer: 9π
Area = πr2 = π × 32 = 9π square centimeters.
Question 5
A circle has radius 4 cm. What is its exact area in square centimeters, written as a multiple of π?
- 64π
- 8π
- 16π
- 18π
A hint
Use the radius, not the diameter, in πr2.
Answer & why
Answer: 16π
Area = πr2 = π × 42 = 16π square centimeters.
Question 6
A circle has radius 5 cm. What is its exact area in square centimeters, written as a multiple of π?
- 100π
- 27π
- 25π
- 10π
A hint
Use the radius, not the diameter, in πr2.
Answer & why
Answer: 25π
Area = πr2 = π × 52 = 25π square centimeters.
Question 7
A circle has radius 6 cm. What is its exact area in square centimeters, written as a multiple of π?
- 36π
- 12π
- 144π
- 38π
A hint
Use the radius, not the diameter, in πr2.
Answer & why
Answer: 36π
Area = πr2 = π × 62 = 36π square centimeters.
Question 8
A circle has radius 7 cm. What is its exact area in square centimeters, written as a multiple of π?
- 14π
- 49π
- 51π
- 196π
A hint
Use the radius, not the diameter, in πr2.
Answer & why
Answer: 49π
Area = πr2 = π × 72 = 49π square centimeters.