Answer: 5 inches.
Explanation:
1. You must use the formula for calculate the area of a circle, which is shown below:
![A=3.14r^(2)](https://img.qammunity.org/2020/formulas/mathematics/high-school/d11ik82vfhshnpeff8gbb7ymfbtll90re7.png)
2. You know the area of the circle, therefore, you can solve for the radius, as following:
![3.14r^(2)=A\\r^(2)=(A)/(3.14)\\r=\sqrt{(A)/(3.14)}](https://img.qammunity.org/2020/formulas/mathematics/high-school/z2vh16vn7sp6lidtmmjahc3vqyny22bf8j.png)
3. Now, you must substitute the value of the area into the equation above. Then, you obtain the following result:
![r=\sqrt{(78.5in^(2))/(3.14)}\\r=5in](https://img.qammunity.org/2020/formulas/mathematics/middle-school/gklemrpnmmhnlfrb2g3k5mn475d6b8ccpc.png)