Area and Circumference of Circles

Front

What is the formula for 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 diameter is twice the radius. d = 2r.

Front

How do you calculate the area of a circle?

Back

A = πr², where A is area and r is radius.

Front

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

Back

10 cm.

Front

If the diameter of a circle is 14 m, what is its radius?

Back

7 m.

Front

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

Back

62.8 cm.

Front

What is the area of a circle with a diameter of 8 m?

Back

50.24 m².

Front

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

Back

5 cm.

Front

What is the value of π (pi) approximately?

Back

3.14.

Front

If the radius of a circle is doubled, how does the area change?

Back

The area increases by a factor of four.