Area and Circumference of Circles

Front

What is the definition of a radius in a circle?

Back

The radius is the distance from the center of the circle to any point on its circumference.

Front

What is the definition of a diameter in a circle?

Back

The diameter is the distance across the circle through its center, equal to twice the radius.

Tags

CCSS.HSG.C.A.2

Front

What is the formula for the circumference of a circle?

Back

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

Tags

CCSS.7.G.B.4

Front

What is the formula for the area of a circle?

Back

A = πr², where r is the radius.

Tags

CCSS.7.G.B.4

Front

If a circle has a radius of 7 cm, what is its diameter?

Back

The diameter is 14 cm (d = 2r).

Tags

CCSS.7.G.B.4

Front

If a circle has a diameter of 20 cm, what is its circumference?

Back

The circumference is 62.83 cm (C = πd = π × 20).

Tags

CCSS.7.G.B.4

Front

If a circle has a radius of 3 inches, what is its area?

Back

The area is 28.27 in² (A = πr² = π × 3²).

Tags

CCSS.7.G.B.4

Front

What do you need to calculate to find out how much fencing is required for a circular playground?

Back

You need to calculate the circumference.

Front

If a cookie has a radius of 5 inches, what is the area that needs to be iced for one cookie?

Back

The area is 78.54 in² (A = πr² = π × 5²).

Tags

CCSS.7.G.B.4

Front

If Danielle wants to ice 3 cookies with a radius of 5 inches each, how much total area must she cover?

Back

The total area is 235.62 in² (3 × 78.54 in²).

Tags

CCSS.7.G.B.4