Skill: Solve elapsed time problems

Elapsed time is how long something lasts from a start time to an end time. A helpful strategy is to count forward in easy parts.

Example: A movie starts at 2:45 p.m. and ends at 4:10 p.m. How long is the movie?

1. Count from 2:45 to the next hour, 3:00:

$$15\text{ minutes}$$

2. Count from 3:00 to 4:00:

$$1\text{ hour}$$

3. Count from 4:00 to 4:10:

$$10\text{ minutes}$$

4. Add the parts:

$$15\text{ minutes}+1\text{ hour}+10\text{ minutes} =1\text{ hour }25\text{ minutes}$$

The movie lasted 1 hour 25 minutes.

Remember that clock minutes are not decimal numbers. Since there are $60$ minutes in $1$ hour, $45$ minutes to $60$ minutes is $15$ minutes, not $0.15$ hours.