Length Qr 4Cddab

1. **Problem Statement:** We need to find the length of the segment $QR$ on a number line where $Q$ is at 16 and $R$ is at 20. 2. **Formula Used:** The length between two points on a number line is given by the absolute difference of their coordinates: $$\text{Length} = |x_2 - x_1|$$ 3. **Apply the formula:** Here, $x_1 = 16$ and $x_2 = 20$. $$\text{Length} = |20 - 16|$$ 4. **Calculate:** $$\text{Length} = |4| = 4$$ 5. **Conclusion:** The length of $QR$ is 4 units.