Hal did not make an error in his procedure. However, the best option that indicates where there might be a misunderstanding in his approximation process is:
In step 4, he made an error in selecting the correct decimal approximation.
While Hal's steps generally lead him to a reasonable approximation of \(\sqrt{82.5}\), the final selection of 9.09 may not be the most precise choice based on the calculations provided.
Specifically, based on the squared values, 9.08 gives 82.44 and 9.09 gives 82.62, so since 82.5 is closer to 82.44, 9.08 would have actually been a better approximation than 9.09—leading to the conclusion that there is a potential misstep in selecting the closest value in the final step.