To determine the percentage of farmers with sandy soil who prefer producing carrots, we will use the formula for relative frequency:
\[ \text{Relative Frequency} = \frac{\text{Number of favorable outcomes}}{\text{Total number of outcomes}} \times 100 \]
In this case, the number of farmers with sandy soil who prefer producing carrots is 120, and the total number of farmers with sandy soil is 170.
Now, we can calculate the percentage:
\[ \text{Relative Frequency} = \frac{120}{170} \times 100 \]
Calculating this gives:
\[ \text{Relative Frequency} = \frac{120}{170} \approx 0.70588 \]
Converting to percentage:
\[ 0.70588 \times 100 \approx 70.6% \]
Thus, the answer is:
70.6%