Circle Area and Circumference Flashcards

Question 1

What is $\pi$ (pi) in circles?

Accepted Answer

$$\pi=\frac{C}{d}$$ The constant ratio of a circle’s circumference $C$ to its diameter $d$ (approximately $3.14159$).

Question 2

State the area formula for a circle.

Accepted Answer

$$A=\pi r^2$$ where $A$ is area and $r$ is radius.

Question 3

What is the perimeter of a semicircle with radius $r$?

Accepted Answer

$$P_{	ext{semi}}=\pi r+2r$$ It’s half the circumference ($\pi r$) plus the diameter ($2r$).

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