Circles

Circles

Learn how how to find the Area and Circumference of Circles when you have the radius or the diameter of the circle.

Step by step guide to solve Circles

  • In a circle, variable \(r\) is usually used for the radius and \(d\) for diameter and \(π\) is about \(3.14\).
  • Area of a circle \(=πr^2\)
  • Circumference of a circle \(=2πr\)

Example 1:

Find the area of the circle.

Solution:

Use area formula: Area \(=πr^2\),
\(r=6\) \(in\), then: Area \(=π(6)^2=36π, π=3.14\) then: Area \(=36×3.14=113.04\) \(in^2\)

Example 2:

Find the Circumference of the circle.

Solution:

Use Circumference formula: Circumference \(=2πr \)
\(r=9 \) \(cm\) , then: Circumference \(=2π(9)=18π \)
\(π=3.14\) then: Circumference \(=18×3.14=56.52\) \(cm\)

Example 3:

Find the area of the circle.

Solution:

Use area formula: Area \(=πr^2\),
\(r=6\) \(in\), then: Area \(=π(4)^2=16π, π=3.14\) then: Area \(=16×3.14=50.24\) \(in^2\)

Example 4:

Find the Circumference of the circle.

Solution:

Use Circumference formula: Circumference \(=2πr \)
\(r=9 \) \(cm\) , then: Circumference \(=2π(6)=12π \)
\(π=3.14\) then: Circumference \(=12×3.14=37.68\) \(cm\)

Exercises

Find the area and circumference of each circle. \((\pi=3.14)\)

Download Circles Worksheet

  1. \(\color{blue}{Area: \ 50.24 \ in^2 , \ Circumference: \ 25.12 \ in}\)
  2. \(\color{blue}{Area: \ 1,017.36 \ cm^2, \ Circumference: \ 113.04 \ cm}\)
  3. \(\color{blue}{Area: \ 78.5 \ m^2, \ Circumference: \ 31.4 \ m}\)
  4. \(\color{blue}{Area: \ 379.94 \ cm^2 , \ Circumference: \ 69.08 \ cm}\)

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