Answer: 5 inches.
Step-by-step explanation:
1. You must use the formula for calculate the area of a circle, which is shown below:
[tex]A=3.14r^{2}[/tex]
2. You know the area of the circle, therefore, you can solve for the radius, as following:
[tex]3.14r^{2}=A\\r^{2}=\frac{A}{3.14}\\r=\sqrt{\frac{A}{3.14}}[/tex]
3. Now, you must substitute the value of the area into the equation above. Then, you obtain the following result:
[tex]r=\sqrt{\frac{78.5in^{2}}{3.14}}\\r=5in[/tex]
