area of a circle

classic Classic list List threaded Threaded
2 messages Options
amy amy
Reply | Threaded
Open this post in threaded view
|

area of a circle

What is the exact area of a circle with a diameter of 21 inches?
AlgebraHouse AlgebraHouse
Reply | Threaded
Open this post in threaded view
|

Re: area of a circle

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