To determine if the relationship between the time walking and the calories burned is proportional, we can look for a constant ratio between the two variables—time and calories burned.
We can calculate the ratio of calories burned to time for each pair:
- For 20 minutes: \( \frac{100 \text{ calories}}{20 \text{ minutes}} = 5 \)
- For 30 minutes: \( \frac{150 \text{ calories}}{30 \text{ minutes}} = 5 \)
- For 40 minutes: \( \frac{200 \text{ calories}}{40 \text{ minutes}} = 5 \)
- For 60 minutes: \( \frac{300 \text{ calories}}{60 \text{ minutes}} = 5 \)
- For 80 minutes: \( \frac{400 \text{ calories}}{80 \text{ minutes}} = 5 \)
Since the ratio of calories burned to time is consistent (always equal to 5), this indicates a proportional relationship.
Also, a proportional relationship passes through the origin, which is evident since when time is 0, the calories burned would equally be 0.
Therefore, the correct response is:
The relationship is proportional.