1. **State the problem:** Harper wants to drive a total of 1600 kilometres but will only drive a maximum of 225 miles each day. We need to find how many whole days Harper will need to complete the trip. 2. **Understand the conversion:** The graph shows a line passing through (0,0) and (25 miles, 40 kilometres). This means 25 miles correspond to 40 kilometres. 3. **Find the conversion factor from miles to kilometres:** $$\text{1 mile} = \frac{40}{25} = 1.6 \text{ kilometres}$$ 4. **Convert the maximum daily driving distance from miles to kilometres:** $$225 \text{ miles} = 225 \times 1.6 = 360 \text{ kilometres}$$ 5. **Calculate the number of days needed:** $$\text{Number of days} = \frac{1600 \text{ kilometres}}{360 \text{ kilometres/day}} \approx 4.44$$ 6. **Since Harper can only drive whole days, round up:** $$\text{Days needed} = 5$$ **Final answer:** Harper will need 5 whole days to complete the 1600 km trip.