Area and Circumference of Circles

Front

What is the formula for finding the circumference of a circle?

Back

C = π·d, where C is the circumference and d is the diameter.

Front

How do you calculate the diameter of a circle if you know the radius?

Back

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

Front

If the radius of a circle is 12.5 meters, what is the diameter?

Back

The diameter is 25 meters.

Front

What is the relationship between the radius and diameter of a circle?

Back

The diameter is always twice the radius.

Front

What is the formula for finding the area of a circle?

Back

A = π·r², where A is the area and r is the radius.

Front

If the diameter of a circle is 50 yards, what is the radius?

Back

The radius is 25 yards.

Front

How do you find the circumference of a circle with a radius of 10 feet?

Back

Use the formula C = 2·π·r. For r = 10 feet, C = 20π feet, approximately 62.83 feet.

Front

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

Back

C = π·d = π·12 cm, approximately 37.68 cm.

Front

What is the value of π (pi) approximately?

Back

π is approximately 3.14.

Front

If a circle has a radius of 5 inches, what is its area?

Back

A = π·r² = π·(5 inches)² = 25π square inches, approximately 78.54 square inches.