Unit 7, Lesson 1
Compare, Count On, and Count Back
Grade 2
Preparation
Lesson Narrative
In a previous unit, students compared three-digit numbers, using a number line, and considered how close they were to one another and their distance from zero. In this lesson, students compare numbers and use the number line to consider ways to find the difference between 2 three-digit numbers. When locating numbers on the number line, students recognize that when the numbers are relatively close, they can simply count on or count back to determine the difference between the two numbers.
In the second activity, students analyze number lines and counting sequences that increase or decrease by 10 or by 100. Using these number relationships, students label number lines by counting on or counting back by 10 or by 100. The work of this activity helps prepare students to use and make sense of computation methods based on counting or adding on by place, in upcoming lessons.
- Engagement
- MLR8
- Identify (orally and in writing) unknown numbers that complete a count by 10 or by 100.
- Interpret (orally) number line diagrams that represent strategies for adding and subtracting within 100.
- Let’s compare numbers and add or subtract.
Required Preparation
None
Teacher Reflection Questions
In previous lessons, students located and compared numbers on the number line. How did the number line help them make sense of subtraction methods based on counting on by place? How could you use number lines to help students make their thinking visible for others?