Subtraction Within 1,000 on the Number Line

Learning Resource Type

Learning Activity

Subject Area

Mathematics

Grade(s)

Overview

Students will use strategies based on place value to subtract in this explore activity. Students will bridge from using a concrete model to using a number line drawing when subtracting within 1,000.

This activity was created as a result of the ALEX Resource Development Summit.

Phase

During/Explore/Explain

Mathematics (2019) Grade(s): 2

MA19.2.12
Add and subtract within 1000 using concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship between addition and subtraction; relate the strategy to a written method.

Vocabulary

Compose
Decompose

Knowledge

Students know:

how to count to 1,000.
how to identify hundreds, tens, and ones.
how to compose numbers.
how to decompose two digit numbers.
how to record strategies for solving addition and subtraction problems.

Skills

Students are able to:

add and subtract within 1000.
model addition problems using visual models.
record strategies for solving addition problems.
communicate the relationship between models and symbolic (numeric) representations.

Understanding

Students understand that:

relationships between models of addition/subtraction problems and written strategies of those models can be used to justify solutions.

Learning Objectives

Students will use strategies based on place value to subtract within 1,000.

Students will use a number line drawing to show the strategy they used to subtract within 1,000.

Activity Details

The teacher will download the presentation Subtraction Within 1,000 on the Number Line.
The teacher and the students will read the learning targets together (Slide 2).
The teacher will place a basket of about 1,000 objects with each group of 4 students. Each student will create a collection of 211 objects. Review efficient counting strategies (Slide 3).
Check to make sure each student has 211 objects. The teacher will present the problem (Slide 4).

The teacher will walk around and observe how the students removed the objects. The teacher should look for three different methods of removal (all ones, tens and ones, etc.) for sharing purposes.
When sharing, the methods/strategies should build on one another starting with the least efficient and moving to the most efficient. The methods/strategies will be modeled on the number line. See Slide 8 for example.
As the student explains their strategy to the class, the teacher will model on the blank number line.
After modeling the strategies on the number line, the students will record the strategy they used to remove the objects on their personal number line recording sheet.
If there are strategies used the teacher did not model, notate on the checklist/notes page. Check with those students as they are recording their strategy to determine if they need assistance.

5. The teacher may choose to project Slides 5, 6, and 7 on a whiteboard or interactive board to model strategies or record on chart paper (Slides 5, 6, 7).

6. The students will recreate their original collection of 211 objects (Slide 9).

7. Repeat steps 4 and 5 (Slides 11, 12, and 13) with the new problem.

8. Close with a discussion of subtraction strategies (Slide 15).

Assessment Strategies

The teacher will use the checklist/notes page to formatively assess during the activity.

Background / Preparation

Download Subtraction Within 1,000 on the Number Line Google Slides Presentation.
Gather a bucket containing close to 1,000 objects for each group of 4 students.
Print one recording sheet per student.
Print multiple copies of the checklist/notes page to use as a formative assessment.
If the teacher prefers to model strategies on chart paper, chart paper and a chart marker will need to be gathered.

https://docs.google.com/presentation/d/1B-kSenW8aGAiL6EJCOTgw0LYuR8s2Rn2a-a6L_n…

Approved Date

2020-08-05

Owner (Author)

jtowles

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