To find the rate at which Sam walked, you can use the formula:
\[ r = \frac{d}{t} \]
where:
- \( r \) is the rate,
- \( d \) is the distance (in kilometers), and
- \( t \) is the time (in minutes).
Given:
- \( d = 4 \) kilometers
- \( t = 50 \) minutes
Now, substituting the values into the formula:
\[ r = \frac{4 \text{ km}}{50 \text{ minutes}} \]
Calculating that gives:
\[ r = 0.08 \text{ km/min} \]
Thus, the rate at which Sam walked is 0.08 kilometers per minute.