Area and circumference

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, where r is the radius.

Front

What is the value of π (pi) approximately?

Back

π ≈ 3.14.

Front

If the radius of a circle is doubled, how does the area change?

Back

The area increases by a factor of four.

Front

If the radius of a circle is 10 cm, what is the area?

Back

Area = π(10)² = 314.16 cm².

Front

If the radius of a circle is 12.5 mm, what is the circumference?

Back

Circumference = 2π(12.5) ≈ 78.5 mm.

Front

What is the relationship between diameter and radius?

Back

Diameter = 2 × Radius.

Front

How do you find the radius if you know the area of a circle?

Back

Radius = √(Area/π).

Front

What is the circumference of a circle with a diameter of 20 cm?

Back

Circumference = π × Diameter = π × 20 ≈ 62.83 cm.

Front

What happens to the circumference if the radius is halved?

Back

The circumference is also halved.