circumference and Area of a Circle

Front

What is the formula for the area of a circle?

Back

A = πr², where A is the area and r is the radius.

Front

What is the formula for the circumference of a circle?

Back

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

Front

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

Back

A = π(10)² = 314.16 cm² (approximately).

Front

If the diameter of a circle is 20 cm, what is the circumference?

Back

C = πd = π(20) = 62.83 cm (approximately).

Front

What is the relationship between diameter and radius?

Back

The diameter is twice the radius: d = 2r.

Front

How do you convert diameter to radius?

Back

Divide the diameter by 2: r = d/2.

Front

What is the circumference of a circle with a radius of 5 inches?

Back

C = 2π(5) = 31.42 inches (approximately).

Front

What is the area of a circle with a radius of 3 cm?

Back

A = π(3)² = 28.27 cm² (approximately).

Front

If a circle has a circumference of 31.4 cm, what is its radius?

Back

r = C/(2π) = 31.4/(2π) = 5 cm.

Front

What is the area of a circle with a diameter of 12 cm?

Back

A = π(6)² = 113.10 cm² (approximately).