To find out how many kilometers Austin hiked each day, you can divide the total distance by the number of days.
Austin hiked a total of 4 kilometers over 2 days:
\[ \text{Distance per day} = \frac{\text{Total distance}}{\text{Number of days}} = \frac{4 \text{ kilometers}}{2 \text{ days}} = 2 \text{ kilometers} \]
So, Austin hiked 2 kilometers each day.