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.

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

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.

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.