*What is the exact area of a circle with a diameter of 21 inches?
*

The formula for the area of a circle is A = πr²

Diameter of a circle is all the way across the circle,

while radius is half way across the circle.

If the diameter of a circle is 21, then the radius is 21/2 {half the diameter}

A = πr²

= 22/7(21/2)² {substituted 22/7 in for π and 21/2 in for radius}

= 22/7(441/4) {squared 21/2 by multiplying it by itself}

=

**693/2 in² **{multiplied 22/7 by 441/4}

*Note*

- Using the fraction 22/7 for π will give a more "exact" answer

* - Algebra House *
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