Finding the Circumference

Front

What is the formula to find the circumference of a circle?

Back

C = π·d or C = 2·π·r, where C is circumference, d is diameter, and r is radius.

Front

If the radius of a circle is 22 inches, what is the diameter?

Back

The diameter is 44 inches, since d = 2·r.

Front

What is the value of π (pi) commonly approximated as?

Back

π is commonly approximated as 3.14.

Front

Calculate the circumference of a circle with a diameter of 44 inches using π = 3.14.

Back

C = π·d = 3.14·44 = 138.16 inches.

Front

What does 'C' represent in the formula C = π·d?

Back

'C' represents the circumference of the circle.

Front

If a circle has a circumference of 78.5 cm, what is its diameter?

Back

The diameter is 25 cm, since d = C/π = 78.5/3.14.

Front

What is the circumference of a circle with a radius of 3.5 feet?

Back

C = 2·π·r = 2·3.14·3.5 = 21.98 feet.

Front

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

Back

C = π·d = 3.14·10 = 31.4 cm.

Front

What is the relationship between radius and diameter?

Back

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

Front

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

Back

The radius is 5 cm, since r = C/(2·π) = 31.4/(2·3.14).