Question 312397
What is the exact area of a circle with a diameter of 15 inches

I think it would be 15pi square inches? 
<pre><b>
No that's the circumference, the distance around the circle,
not the area, which is the amount of space inside the circle:
You found {{{C=pi*d=pi*15=15pi}}} inches, though the circumference 
would be in inches, not square inches

You don't want the circumference, you want the area, which is
found by the formula {{{A=pi*r^2}}}

To find the area, we need the radius, not the diameter.
The radius is {{{1/2}}} of the diameter.

So the radius is {{{1/2}}}{{{"×"}}}{{{15}}} or {{{15/2}}}

Substituting {{{15/2}}} for {{{r}}} in the formula for the area of a circle:

{{{A = pi*r^2}}} 
{{{A = pi(15/2)^2}}}
{{{A = pi*(225/4)}}}
{{{A=225pi/4}}} square inches or about 176.7 square inches.

Edwin</pre>