Solve Problems Involving Time (Part 1)

10 min

Narrative

The purpose of this Choral Count is to invite students to practice counting times by 15 minutes and notice patterns in the count. This will be helpful later in this section when students will solve problems involving addition and subtraction of time intervals.

Students have an opportunity to notice regularity through repeated reasoning (MP8) as they count by 15 minutes over a span of 3 hours.

Launch

  • “Count by 15 minutes, starting at 12:00.”
  • Record as students count. Record times in the count in a single column.
  • Stop counting and recording at 3:00.
Teacher Instructions
  • “What patterns do you see?”
  • 1–2 minutes: quiet think time
  • Record responses.
Solution Steps (3)
  1. 1
    Count by 15 minutes starting at 12:00
    →12:00, 12:15, 12:30, 12:45, 1:00, 1:15, 1:30, 1:45, 2:00, 2:15, 2:30, 2:45, 3:00
  2. 2
    Notice patterns in the count
    →Minutes follow 00, 15, 30, 45 pattern; every 4 counts of 15 = 1 hour
  3. 3
    Calculate elapsed time between two times
    →From 1:15 to 1:45 is 30 minutes (2 jumps of 15); from 1:15 to 2:30 is 75 minutes (5 jumps of 15)

Sample Response

Sample responses:
  • Every 4 counts of 15 minutes is a new hour.
  • Three hours pass during the count because we go from 12:00 to 3:00.
  • The minutes have a pattern of 00, 15, 30, 45, then back to 00, which is the next hour.
Activity Synthesis (Teacher Notes)
  • “How much time passed between 1:15 and 1:45?” (30 minutes) “1:15 and 2:30?” (75 minutes, or 1 hour 15 minutes)
  • Consider asking:
    • “Who can restate the pattern in different words?”
    • “Does anyone want to add an observation on why that pattern is happening here?”
    • “Do you agree or disagree? Why?”
Standards
Addressing
  • 3.MD.1·Tell and write time to the nearest minute and measure time intervals in minutes. Solve word problems involving addition and subtraction of time intervals in minutes, e.g., by representing the problem on a number line diagram.
  • 3.MD.A.1·Tell and write time to the nearest minute and measure time intervals in minutes. Solve word problems involving addition and subtraction of time intervals in minutes, e.g., by representing the problem on a number line diagram.

25 min

10 min