Circles: Circumference and Area

Front

What is the formula for the circumference of a circle?

Back

C = πd or C = 2πr, where C is the circumference, 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 A is the area and r is the radius.

Tags

CCSS.7.G.B.4

Front

If a circle has a diameter of 10 cm, what is its radius?

Back

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

Tags

CCSS.7.G.B.4

Front

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

Back

C = 2π(7) = 14π ≈ 43.98 cm.

Tags

CCSS.7.G.B.4

Front

What is the area of a circle with a radius of 4 cm?

Back

A = π(4)² = 16π ≈ 50.27 cm².

Tags

CCSS.7.G.B.4

Front

What is the diameter of a circle if its radius is 12 cm?

Back

The diameter is 24 cm, since the diameter is twice the radius.

Tags

CCSS.7.G.B.4

Front

How do you find the circumference of a circle using the radius?

Back

Use the formula C = 2πr.

Tags

CCSS.7.G.B.4

Front

What is the relationship between diameter and radius?

Back

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

Tags

CCSS.7.G.B.4

Front

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

Back

r = C/(2π) = 31.4/(2π) ≈ 5 cm.

Tags

CCSS.7.G.B.4

Front

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

Back

A = π(5)² = 25π ≈ 78.54 cm².

Tags

CCSS.7.G.B.4