Area and Circumference of Circles

Front

What is the formula for the circumference of a circle?

Back

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

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

If the radius of a circle is 5 cm, what is the circumference?

Back

C = 2π(5) = 10π ≈ 31.4 cm.

Front

What is the radius of a circle?

Back

The radius is the measurement from the center of the circle to any point on its edge.

Front

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

Back

Use the formula d = C/π.

Front

What is π (pi)?

Back

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

Front

If a circle has a circumference of 62.8 cm, what is its diameter?

Back

d = C/π = 62.8/3.14 = 20 cm.

Front

What is the area of a circle?

Back

A = πr², where r is the radius.

Front

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

Back

The radius is 5 cm, which is half of the diameter.

Front

How do you calculate the circumference of a circle with a diameter of 15 mm?

Back

C = πd = π(15) = 15π mm.