1. Measuring Elapsed Time

2. Units of Time 1 minute (min) = 60 seconds (s) 1 hour (h) = 60 minutes 1 day = 24 h 1 week (wk) = 7 days 1 year is about 365 days 1 year is about 52 weeks

3. Add or Subtract 3 h 15 min 52 sec 1 h 42 min 11sec + 5 h 5min 29 sec 3 h 15 min 52 sec _ 63 sec _ 60 sec

4. Elapsed time The time between two events is called elapsed time. If both times are AM, or both times are PM, then just subtract the times. Be careful when times pass midnight or noon.

5. Example: Find the elapsed time between 1:45 PM and 5:27 PM 5:275 h 27 min 1:45 1 h 45 min 4 1 h = 60 min 87 3 h 42 min

6. How long is a school day that goes from 8:15 AM to 3:25 PM? When one time is in the morning, and one is in the afternoon, add 12 hours to the end-time. This takes care of passing from AM to PM. 3 hours 25 min15 hours 25 min 8 hours 15 min 7 hours 10 min

7. Counting Up Another way to deal with elapsed time that includes both AM and PM is to “count up.” Add hours and minutes at the end. Example: How much time is between 5:45 AM and 7:20 PM? 5:45 to 6:00 15 min 6:00 to 12:00 6 h 12:00 to 7:00 7 h 7:00 to 7:20 20 min Combine minutes with minutes: 15 + 20 = 35 min Combine hours with hours: 6 + 7 = 13 h Answer: 13 hours and 35 minutes.