One Less!
Lesson 3 of 13
Objective: SWBAT use a variety of strategies to identify numbers that are one less.
Setting Up the Learning
This is the first time students are encountering more and less/fewer. I started with less/fewer because it tends to be the more difficult!
Review
We have been working on reading and writing all of our numbers. We learned lots of strategies last week to help us remember how to write numbers!
Connect
When we do math in real life, we often have problems where we take away just 1 of something. Learning what numbers are 1 less will help us put a number line in our brain and help us solve these kind of problems easier.
Objective : Your thinking job today is: What does “one less” mean?
Opening Discussion
The words less and fewer are very important in math. They both mean you take some away. For example, if I have 4 cookies, and Ms. Anderson has 5 cookies, I have fewer. Less and fewer always means smaller. (I'll introduce a hand motion here for these terms! See video for more info on hand motions!)

Practice the meaning of 1 less:
Model meaning on a number line:
Present problem: I have 15 crackers. I dropped one, so now I have 1 less than 15. How many crackers do I have now?

Resources (1)
Resources (1)
Resources
Student Work Time and Share
Student Work Time:
While students work, I'll look for different ways students solve, particularly a student who solves with cubes and one that solves with a number line. This is important because CCSS emphasizes less teacher modeling, more student thinking! I don't model how to figure this out because I need to see how students solve first so we can share out the different strategies.
This is also aligned to MP5, Use appropriate tools strategically. Students have to choose their own tool and explain how to use it. When we move into the strategy share, they have to be able to articulate how others used tools to solve the problem.
Student Share:
I'll share a cubes strategy and a number line strategy, asking guiding questions throughout.
 How are these strategies the same? How are they different?
 How did we show that we took away 1 on the number line?
See picture of strategy share chart!!
Game Practice:
I'll model the game a few times and then practice the game whole group with students.
Game Rules:
1. Pull a number card.
2. Build the number with cubes on your gameboard.
3. Write down your number.
4. Show one less!
5. Start over!
Resources (1)
Resources (1)
Resources
Independent Practice
Students play the game, but possibly with different numbers based on their level of understanding. Differentiating this game is very important because students who struggle with basic counting will get quickly overwhelmed by numbers to 40. Keep those kids at lower numbers for now so they learn the concept.
Group A: Intervention
Students play the game with numbers under 20. Students use cubes to practice concretely with one less.
Group B: Right On Track
Students play the game with numbers under 40. Students use cubes to practice concretely with one less if needed, but then model what they did on the number line.
Group C: Extension
Students play the game with numbers under 40. Students do not have cube support, but do have the number line.
*See attached document for recording sheet and game cards.
Resources (1)
Resources (1)
Resources
Closing
Today our thinking job was: What does “one less” mean? We saw that one less means to take away 1, it means our number is getting smaller by 1. To set students up to use the number line only in the next day's lesson, we will do a quick number line and cube connection activity: "Let’s start at 20, and do one less until we get to 0! (T does a quick cube activity, while another child points to the numbers on the number line. Start at 20, what’s one less? 19! Now we have 19, what’s one less? 18!)" 
Similar Lessons
Counting by ones to 120
Environment: Urban
Learning To Be A Friendly Partner
Environment: Suburban
Kicking Off the Year With Counting
Environment: Urban
 UNIT 1: Creating a Culture of Math
 UNIT 2: Count to 100 Every Day!
 UNIT 3: 10: A First Grader's Best Friend
 UNIT 4: Charting and Analyzing Data
 UNIT 5: Inch by Inch, Paperclip by Paperclip
 UNIT 6: Properties of Addition and Subtraction
 UNIT 7: Shapes and Blocks
 UNIT 8: Understanding Equality
 UNIT 9: Adding and Subtracting: Base Ten
 UNIT 10: Solving 3 Addend Problems
 UNIT 11: Missing Parts: Unknowns in All Positions
 UNIT 12: Parts of a Whole
 UNIT 13: Tick Tock, Tick Tock
 UNIT 14: Time is Money: Hitting all the MD Standards
 UNIT 15: Base 10 Bonanza
 UNIT 16: What the WHAT?! Teaching Challenging Story Problems
 LESSON 1: Missing Numbers to 50
 LESSON 2: Counting Strips
 LESSON 3: One Less!
 LESSON 4: One More/One Less Hop
 LESSON 5: Missing Numbers
 LESSON 6: Number Puzzles
 LESSON 7: Counting Collections
 LESSON 8: Counting Collections: 100 Objects
 LESSON 9: Constructing Tens and Ones
 LESSON 10: Building Tens at the Lego Factory
 LESSON 11: It's Elementary My Dear Watson
 LESSON 12: Down on the Farm: Base 10 Problems
 LESSON 13: WANTED: Runaway Number