Lessons · Quantitative Reasoning
CLT Quantitative Reasoning · Lesson
Circles
Area is πr², circumference is 2πr. An arc or sector is a fraction of the whole: the central angle over 360°.
- Find the radius first. If you are given the diameter, halve it.
- For an arc length, multiply the circumference by angle ÷ 360.
- For a sector area, multiply the area by angle ÷ 360.
Q. A circle has radius 6. How long is the arc cut off by a 60° central angle?
Answer 2π
Circumference = 12π; 60 ÷ 360 = 1/6; 12π ÷ 6 = 2π.
- Using the diameter in πr².
- Mixing up arc length (a part of 2πr) and sector area (a part of πr²).
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