Circles: Circumference and Area

Front

What is the formula for the circumference of a circle?

Back

C = πd or C = 2πr

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 radius of a circle?

Back

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

Front

How do you calculate the area of a circle?

Back

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

Front

What is π (pi)?

Back

π (pi) is a mathematical constant approximately equal to 3.14, representing the ratio of the circumference of a circle to its diameter.

Front

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

Back

C = 2πr = 2π(7) ≈ 43.98 inches.

Front

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

Back

r = d/2 = 10/2 = 5 cm.

Front

What is the area of a circle with a radius of 4 units?

Back

A = πr² = π(4)² = 16π ≈ 50.27 square units.

Front

What is the relationship between diameter and radius?

Back

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

Front

What is the circumference of a circle with a diameter of 12 inches?

Back

C = πd = π(12) ≈ 37.68 inches.