1. **State the problem:** We need to find the speed of the boat between 30 and 50 seconds after starting using the distance-time graph. 2. **Recall the formula for speed:** Speed is the rate of change of distance with respect to time, given by $$\text{Speed} = \frac{\text{Change in distance}}{\text{Change in time}} = \frac{\Delta d}{\Delta t}$$ 3. **Identify the points on the graph:** From the graph description, at 30 seconds, the distance is approximately 240 meters, and at 50 seconds, the distance is approximately 480 meters. 4. **Calculate the change in distance and time:** $$\Delta d = 480 - 240 = 240 \text{ meters}$$ $$\Delta t = 50 - 30 = 20 \text{ seconds}$$ 5. **Calculate the speed:** $$\text{Speed} = \frac{240}{20} = 12 \text{ meters per second}$$ 6. **Interpretation:** The boat's speed between 30 and 50 seconds was 12 meters per second.