To convert miles per hour (mph) to miles per minute (mpm), you need to divide the speed in miles per hour by the number of minutes in an hour.
There are 60 minutes in an hour, so you divide by 60.
For your example of 50 miles per hour, the conversion to miles per minute would be:
\[ \text{Miles per minute} = \frac{50 \text{ miles}}{60 \text{ minutes}} \]
Therefore, the value that can be entered in the box to correctly make this conversion is 60.