In grade 4 students are expected to:
- estimate, measure and record time intervals to the minute,
- determine elapsed time to 5 minute intervals, with and without timelines,
- understand and work with the relationship between years, decades, and centuries.
The use of timelines is frequently not appreciated or understood. It builds nicely from open number line work in grades 2 and 3. The use of the timeline is a good visual scaffold and should be done before determining elapsed time abstractly.
Basically it looks like this.
|How much time has elapsed between 10:35 and 2:15? Mark both times on an open numberline.|
|Mark the next hours that are closest as anchors.|
|Mark the time between the beginning and end times and the added anchors. The total elapsed time is the total of the pieces: 3 hours + 15 minutes + 25 minutes, or 3 hours 40 minutes.|
|If a student isn’t comfortable working across the 12 hour mark, it’s a lot like bridging ten. They could just add an extra anchor of 12 o’clock as drawn to the right.|
To work effectively with elapsed time, students will need several additional subskills. Two of these are bonds of 12 and 60. These bonds closely parallel bonds of ten learned in grade 1 – teachers may want to read that section to get a deeper background. Basically, they need to know the different numbers that add to 12: 1+11, 2+1, 3+9, etc. The bonds of 60 they should work with in grade 4 are 5 + 55, 10 + 50, 15 + 45, and all the others that are multiples of 5 minutes.
A quick exercise where students loop together numbers that add to 60.