Circumference of Circles

Front

What is the formula for 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

What does π (pi) represent in mathematics?

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

Back

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

Front

What is the circumference of a circle with a radius of 7 cm?

Back

C = 2·π·7 = 43.96 cm (approximately).

Front

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

Back

The letter 'd' represents the diameter of the circle.

Front

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

Back

The diameter is 10 cm, since C = π·d, thus d = C/π.

Front

What is the relationship between radius and diameter?

Back

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

Front

How do you calculate the circumference if you only know the radius?

Back

Use the formula C = 2·π·r.

Front

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

Back

C = π·12 = 37.68 cm (approximately).

Front

If the radius of a circle is 3 ft, what is the circumference?

Back

C = 2·π·3 = 18.84 ft (approximately).