



 
Hi, I am going to answer a similar question.
The key here is to know an expression that links the perimeter and radius of a circle. If $P$ is the perimeter of a circle of radius $r$ then \[P = 2 \pi \; r.\] Solving this equation for $r$ yields \[r = \frac{P}{2 \pi}.\] Thus if you know the perimeter you can calculate the radius. Now try to see how you can calculate the radius of a circle if you know the area. Penny  


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