Question 848646
What is the approximate area of a circle with a circumference of 15 in.?

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First use the circumference to find the radius



{{{C = 2*pi*r}}}



{{{15 = 2*pi*r}}}



{{{15/(2*pi) = r}}}



{{{r = 15/(2*pi)}}} ... I'll leave it in its exact form.



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Now use this radius to find the area



{{{A = pi*r^2}}}



{{{A = pi*(15/(2*pi))^2}}}



{{{A = pi*(225/(4*pi^2))}}}



{{{A = (225pi)/(4*pi^2)}}}



{{{A = (225)/(4pi)}}} <--- This is the exact area in terms of {{{pi}}}



{{{A = 17.9049310978382}}} <--- This is the approximate area, which is the <font size=4 color="red">final answer</font><font size=5 color="blue">*</font> they want.



Notes: 


<font size=5 color="blue">*</font> Be sure to follow any rounding rules given (eg: "round to the nearest hundredth")


* Much of this problem can be done without a calculator, but you will need a calculator for that last step (to get the approximate answer).


* The units of the final answer are "square inches"