Group Counting

For today’s Math Talk, students will engage in group counting. Take turns having students share the answer as you count by 9s. In your first time through, start at 9. As students share the next number in the count sequence, record the numbers on the board in vertical columns. After 10-15 numbers in the count sequence have been shared, ask students what they observe.

Students might state the following:

• The numbers are always going up.
• The number in the ones column is always going down one.
• The number in the tens is going up 1.
• Once you get to 0 in the ones, the pattern changes.
• It is like adding ten every time, but then taking away one.
• And many more…

If students are still actively listening and participating, engage in a second group count. This time, choose a number between 1 and 10 that is not 9.

Count up to 15 numbers in the sequence and ask students to make observations about the pattern.

Facilitator Notes

Assuming students are able to count by 10s with automaticity, asking students to count by 9s encourages them to intuitively count by 10s and subtract 1 each time. This is helpful to begin emerging the big idea of the distributive property over subtraction which will be a helpful big idea to use for the Sense Making portion of today’s lesson.

For example, students who do not yet have automaticity counting by 9s might be using this strategy (often in their mind):

• Thinks: 9, Says: 9
• Thinks: 9 + (10 – 1), or 19 – 1, Says: 18
• Thinks: 18 + (10 – 1) or 28 – 1, Says: 27
• And so on…

By engaging in this group counting activity, the idea of distributive property over subtraction may begin emerging through the later portion of this lesson.