Circumference and Area of Circles

Front

What is the formula for the area of a circle?

Back

Area = πr², where r is the radius.

Front

What is the formula for the circumference of a circle?

Back

Circumference = 2πr or Circumference = πd, where d is the diameter.

Front

If the radius of a circle is 3, what is the area?

Back

Area = π(3)² = 9π.

Front

If the diameter of a circle is 20, what is the radius?

Back

Radius = Diameter / 2 = 20 / 2 = 10.

Front

What is the relationship between diameter and radius?

Back

Diameter = 2 × Radius.

Front

How do you convert diameter to radius?

Back

Divide the diameter by 2.

Front

What is the approximate value of π?

Back

π is approximately 3.14.

Front

If the radius of a circle is 6, what is the circumference?

Back

Circumference = 2π(6) = 12π.

Front

What is the area of a circle with a radius of 2?

Back

Area = π(2)² = 4π.

Front

How do you find the circumference if you know the area?

Back

First, find the radius using Area = πr², then use Circumference = 2πr.