Multiplication Expressions

10 min

Narrative

The purpose of this Choral Count is for students to practice counting by 5 and 2 and notice patterns in the count. These understandings help students begin to develop fluency and will be helpful later in this lesson when students write multiplication expressions. When students notice patterns in the count, such as the digit in the ones place alternates between 0 and 5 when counting by 5, they look for and express regularity in repeated reasoning (MP8).

This is the first time students experience the Choral Count routine in grade 3. Students should be familiar with this routine from a previous grade. However, they may benefit from a brief review of the steps involved.

Launch

  • "Count by 5, starting at 0."
  • Record as students count. See Student Responses for recording structure.
  • Stop counting and recording at 50.
Teacher Instructions
  • "What patterns do you see?"
  • 1–2 minutes: quiet think time
  • Record responses.
  • Repeat activity. Count by 2, starting at 0 and stopping at 20.

Student Task

Count by 5, starting at 0 and stopping at 50. Count by 2, starting at 0 and stopping at 20. What patterns do you notice?

Solution Steps (4)
  1. 1
    Count by 5s from 0 to 50
    →0, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50
  2. 2
    Notice pattern in 5s sequence
    →Ones digit alternates 0, 5; tens digit changes every 2 counts
  3. 3
    Count by 2s from 0 to 20
    →0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20
  4. 4
    Notice pattern in 2s sequence
    →Ones digit cycles 0, 2, 4, 6, 8; tens digit changes every 5 counts

Sample Response

0 0
5 2
10 4
15 6
20 8
25 10
30 12
35 14
40 16
45 18
50 20

Sample responses:

In the fives column:

  • The digit in the ones place alternates 0 and 5.
  • The digit in the tens place changes after every 2 counts.

In the twos column:

  • The digit in the ones place counts 0, 2, 4, 6, 8, then repeats.
  • The digit in the tens place changes after 5 counts.
Activity Synthesis (Teacher Notes)
  • "How could some of the patterns help you with counting by these numbers?" (I know that the next count by 5 should end in 5. I know that the next count by 2 should have a 2 in the ones place.)
  • 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.OA.1·Interpret products of whole numbers, e.g., interpret 5 × 7 as the total number of objects in 5 groups of 7 objects each. <em>For example, describe a context in which a total number of objects can be expressed as 5 × 7.</em>
  • 3.OA.A.1·Interpret products of whole numbers, e.g., interpret <span class="math">\(5 \times 7\)</span> as the total number of objects in 5 groups of 7 objects each. <span>For example, describe a context in which a total number of objects can be expressed as <span class="math">\(5 \times 7\)</span>.</span>

10 min

15 min

10 min