Virginia SOL Math / Grade 6 / Measurement & Geometry

6.MG.1

Circumference & Area of Circles

What you'll learn

  • Identify the radius, diameter, and center of a circle
  • Find the circumference of a circle
  • Find the area of a circle

Words to know

Radius —
the distance from the center to the edge of a circle
Diameter —
the distance across a circle through the center
Circumference —
the distance around a circle
Pi —
the ratio of circumference to diameter, about 3.14
Area —
the amount of space a shape covers

Why it matters Wheels, plates, pipes, and pools are circular, so finding distance around and space inside helps us build and measure them.

Worked examples

Model ItI do

Find the circumference of a circle with radius 5 cm. Use pi as 3.14.

Circumference equals pi times the diameter, and the diameter is 2 times 5 = 10 cm. So C = 3.14 times 10 = 31.4 cm.

Try It TogetherWe do

Find the area of a circle with radius 3 in. Use pi as 3.14.

Area equals pi times the radius squared: 3 squared = 9, so A = 3.14 times 9 = 28.26 square inches.

Now YouYou do

Find the circumference of a circle with diameter 8 m. Use pi as 3.14.

Multiply pi by the diameter. Check your answer in the back of this chapter.

Practice

Mastered 0 of 11

Warm-up

Ease in with the basics.

  1. 1.A circle has a radius of 5 cm. What is its diameter?

  2. 2.A circle has a diameter of 12 in. What is its radius?

  3. 3.Find the circumference of a circle with diameter 5 m. Use pi as 3.14.

On Level

The core Quick Check from the book.

  1. 1.A circle has a diameter of 6 cm. What is its radius?

  2. 2.Find the circumference of a circle with diameter 10 ft. Use pi as 3.14.

  3. 3.Find the area of a circle with radius 2 m. Use pi as 3.14.

  4. 4.A circle has a radius of 7 in. What is its diameter?

  5. 5.Find the circumference of a circle with radius 4 cm. Use pi as 3.14.

Challenge

Stretch your thinking.

  1. 1.Find the area of a circle with diameter 10 cm. Use pi as 3.14.

  2. 2.Find the circumference of a circle with radius 6 in. Use pi as 3.14.

  3. 3.A circular garden has a radius of 10 ft. What is its area? Use pi as 3.14.