standard_description: Given a two-digit number, mentally find 10 more or 10 less than the number, without having to count; explain the reasoning used.
problem_activity: Narrative
The purpose of this activity is for students to learn stage 2 of the Write Numbers center. Like the last stage of this center, students take turns writing the next one, two, or three numbers. The player who writes the last number on the board wins. Students may choose to count forward or backward. In this stage, students count by 10 starting at numbers other than 10.
MLR8 Discussion Supports.
Revoice student ideas to demonstrate and amplify mathematical language use. For example, revoice the student statement “the first number changes” as “the number in the tens place increases by one.”
Advances: Speaking
Required Materials
Materials to Gather
Dry erase markers
Sheet protectors
Materials to Copy
Write the Number Stage 2 Gameboard
Required Preparation
Put each gameboard in a sheet protector.
Launch
Groups of 2
Give each group a gameboard and a dry erase marker.
“We are going to learn a new way to do the Write Numbers center.”
Display the gameboard.
“You and your partner will practice writing numbers. Just like the last time we played this game, you will fill in the number path on the gameboard. You can decide to start with the smaller number and count forward, or start with the larger number and count backward. On each turn, you can decide whether you would like to write one, two, or three numbers on the gameboard. The person who writes the last number on the board is the winner.”
“Today you will not write every number in the sequence. You will count by ten and write each number you say.”
Demonstrate playing one round with the students.
“Now you will play with your partner.”
Activity
10 minutes: partner work time
Activity Synthesis
“What do you notice about each number on the gameboard?” (They all have the same amount of ones. The tens go up by one in each number.)


aligns: no