Circumference of Circles

Front

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

Back

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

Front

What is the relationship between diameter and radius?

Back

The radius is half of the diameter. r = d/2.

Front

If the diameter of a circle is 15 cm, what is the radius?

Back

7.5 cm

Front

What is the value of π (pi) approximately?

Back

π is approximately 3.14.

Front

How do you find the difference in circumference between two circles?

Back

Calculate the circumference of each circle using C = πd, then subtract the smaller circumference from the larger.

Front

What is the diameter of a circle with a radius of 10 cm?

Back

20 cm

Front

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

Back

10 cm (C = πd, so d = C/π).

Front

What is the circumference of a circle with a radius of 5 cm?

Back

31.4 cm (C = 2πr).

Front

What is the diameter of a circle if its circumference is 62.8 cm?

Back

20 cm (d = C/π).

Front

If the radius of a circle is doubled, what happens to the circumference?

Back

The circumference also doubles.