To determine the sign of the product \( -16.8 \times \frac{3}{7} \):
- The number \( -16.8 \) is negative.
- The number \( \frac{3}{7} \) is positive.
When you multiply a negative number by a positive number, the result is negative.
Therefore, the sign of the product \( -16.8 \times \frac{3}{7} \) is negative.