To calculate the percentage of students in the sample who reported math as their favorite subject, we use the following formula:
\[ \text{Percentage} = \left( \frac{\text{Number of students who chose math}}{\text{Total number of students surveyed}} \right) \times 100 \]
From the data provided:
- Number of students who chose Math = 4
- Total number of students surveyed = 21
Now, substituting the values into the formula:
\[ \text{Percentage} = \left( \frac{4}{21} \right) \times 100 \approx 19.05 \]
Rounding this to the nearest whole number:
\[ \text{Percentage} \approx 19 \]
Thus, the percentage of students who reported math as their favorite subject is 19.