Circumference & Area of Circles

Front

What is the formula for the circumference of a circle?

Back

C = 2πr or C = πd, where r is the radius and d is the diameter.

Front

What is the formula for the area of a circle?

Back

A = πr², where r is the radius.

Front

Define a chord in a circle.

Back

A chord is a line segment with both endpoints on the circle.

Front

What is the difference between the diameter and the radius of a circle?

Back

The diameter is twice the length of the radius; d = 2r.

Front

How do you calculate the radius if you know the circumference?

Back

r = C / (2π).

Front

How do you calculate the radius if you know the area?

Back

r = √(A/π).

Front

What is the relationship between the radius and the diameter?

Back

The diameter is equal to twice the radius (d = 2r).

Front

What is the value of π (pi) to two decimal places?

Back

π ≈ 3.14.

Front

If the radius of a circle is 7 cm, what is the circumference?

Back

C = 2π(7) ≈ 43.98 cm.

Front

If the radius of a circle is 7 cm, what is the area?

Back

A = π(7)² ≈ 153.94 cm².