Name: _____________________________
Remember: 60 seconds in a minute, 60 minutes in an hour, 24 hours in a day.
How to add and subtract time.
Suppose Rilie studies from 3:48 to 7:05, how would you go about calculating how long he studied?
One way is to do addition. He studies 12 minutes to get to 4:00, plus 3 hours to get to 7:00, plus 5 minutes to get to 7:05, for a total of 3:17. This same method can be extended to include seconds, or even days and years.
The other way is to do subtraction, but there's a catch. You have to be careful when borrowing between different units.
| 7:05 | -> | 6:65 |
| -3:48 | -3:48 | |
| ------- | ------- | |
| 3:17 |
Notice how, when we borrowed from the hour, we only got 60, not 100 as we would have if we were subtracting 348 from 705.
Practice:
4 runners want to recreate the run from Marathon to the Acropolis in Athens. The each leave at 7:45am. Use the runners finish time to calculate the elapsed time
| Finish Time | Elapsed Time | |
|---|---|---|
| Runner 1 | 10:52 | ______________________________ |
| Runner 2 | 10:34 | ______________________________ |
| Runner 3 | 12:14 | ______________________________ |
| Runner 4 | 12:05 | ______________________________ |
Which runner is the fastest?
Which runners took more that 4 hours?
In your groups, try these activities, and come up with some of your own. Each person in the group should try these and have a partner record the start and end times.
| Activity | Estimate | Start time | End time | Elapsed time |
|---|---|---|---|---|
| 1. Sing Jingle Bells | ||||
| 2 10 Jumping Jacks | ||||
| 3. Walk across the classroom | ||||
| 4. | ||||
| 5. | ||||
| 6. | ||||
| 7. | ||||
| 8. |
Extend your thinking:
Including washrooms, there are about 7 rooms between us and the office. Calculate how long it would take you to walk to the office.