Skill: Find elapsed time in whole hours

To find elapsed time in whole hours, count how many one-hour jumps it takes to get from the starting time to the ending time.

Example: A movie starts at $3{:}00$ and ends at $7{:}00$. How long is the movie?

1. Start at $3{:}00$.
2. Count forward one hour at a time:
   • $3{:}00$ to $4{:}00$ = 1 hour
   • $4{:}00$ to $5{:}00$ = 2 hours
   • $5{:}00$ to $6{:}00$ = 3 hours
   • $6{:}00$ to $7{:}00$ = 4 hours
3. The elapsed time is the number of jumps.

$$\boxed{4\text{ hours}}$$

So, the movie lasts 4 hours.