



 
Hi, The area $A$ of a circle is given by \[A = \pi\; r^2\] where $r$ is the radius of the circle and you are told to approximate $\pi$ by 3.14. Similarly the circumference $C$ of a circle is given by \[C = 2 \pi\; r.\] Hence to determine the area and circumference of a circle you need to find its radius $r.$ The square piece of felt that Tye needs to cut has an area of 81 square inches. The area of a square is the square of a side length, and since $9\times 9 = 9^2 = 81,$ his square piece of felt has a side length if 9 inches. Here is my diagram of Tye's square of felt with the largest circle possible drawn on it. What is the radius of the circle? Write back if you need more assistance, 



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