We can use the formula \( r=\sqrt{\frac{S}{12.6}} \) to relate a ball's surface area \( S \) (in square inches) to its radius \( r \) (in inches). Suppose a ball has a surface area of 138.6 square inches. What is its radius? Round your answer to the nearest tenth.

To find the radius \( r \), we can plug the surface area \( S = 138.6 \) into the formula: \[ r = \sqrt{\frac{138.6}{12.6}} \] Calculating the fraction gives us: \[ \frac{138.6}{12.6} = 11 \] Now, taking the square root: \[ r = \sqrt{11} \approx 3.31662479 \] Rounding this to the nearest tenth, the radius \( r \) is approximately \( 3.3 \) inches.