Circumference and Area of a Circle


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In this lesson, we are required to find both the circumference and the area of the circle given its radius or diameter.

Formulas to find the circumference and the area of a circle

  • Circumference of a circle is given by the formula C = 2πr where π = 3.14 and r is the radius of the circle

  • Area of a circle is given by the formula A = πr2 where π = 3.14 and r is the radius of the circle.

Find the area and circumference of following circle. Use π = 3.14

Area Circumference Example 1

Solution

Step 1:

Given radius r = 9.5 units

Step 2:

Circumference of Circle, C = 2πr = 2(3.14)9.5 = 59.66 units

Step 3:

Area of Circle, A = πr2 = (3.14)(9.5)(9.5) = 283.39 square units

Find the area and circumference of following circle. Use π = 3.14

Area Circumference Example 2

Solution

Step 1:

Given diameter = 4; radius r = 4/2 = 2 units

Step 2:

Circumference of Circle, C = 2πr = 2(3.14)2 = 12.56 units

Step 3:

Area of Circle, A = πr2 = (3.14)(2)(2) = 12.56 square units

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