Question 821236
 A circle has area 84 sq. in. Find the radius. 
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You still use the same formula
{{{pi*r^2}}} = 84
Divide both sides by pi
{{{r^2}}} = {{{84/pi}}}
{{{r^2}}} = 26.738
Find the square root of both sides
r = {{{sqrt(26.738)}}}
r = 5.17
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Check on your calc: enter {{{pi*5.17^2}}} 83.97 ~ 84