To find the percentage of rocky-soil farmers who prefer growing peppers, we can use the following formula for relative frequency:
\[ \text{Relative Frequency} = \frac{\text{Number of farmers choosing peppers}}{\text{Total number of rocky-soil farmers}} \]
From the table provided:
- Number of rocky-soil farmers who chose peppers = 150
- Total number of rocky-soil farmers = 250
Now we can plug these numbers into the formula:
\[ \text{Relative Frequency} = \frac{150}{250} = 0.6 \]
To express this as a percentage, multiply by 100:
\[ 0.6 \times 100 = 60% \]
Therefore, the percentage chance that farmers with rocky soil prefer growing peppers is \( \boxed{60.0%} \).