Area and Circumference of a Circle

Front

What is the diameter of a circle?

Back

The diameter is the distance across the circle through its center, equal to twice the radius.

Front

What is the formula for the circumference of a circle?

Back

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

Front

What is the circumference of a circle with a diameter of 28 inches?

Back

C = πd = π(28) ≈ 87.96 inches, rounded to 88 inches.

Front

What is the area of a circle with a radius of 5 cm?

Back

A = πr² = π(5)² = 25π ≈ 78.5 cm².

Front

What is the radius of a circle?

Back

The radius is the distance from the center of the circle to any point on its circumference.

Front

What is the relationship between diameter and radius?

Back

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

Front

What is the area of a circle with a diameter of 10 cm?

Back

A = πr² = π(5)² = 25π ≈ 78.5 cm².

Front

What does circumference measure?

Back

Circumference measures the distance around a circle.

Front

What is the formula for the area of a circle given the diameter?

Back

A = π(d/2)² = (π/4)d².

Front

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

Back

The diameter is 14 cm (d = 2r).