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Table of Contents
Learn the different ways of solving addition and subtraction problems by learning about the different strategies of these operations.
See the fact file below for more information on strategies to add and subtract or alternatively, you can download our 29-page Numbers & Operations in Base 10: Strategies to Add & Subtract worksheet pack to utilise within the classroom or home environment.
Key Facts & Information
Learning Objective
At the end of the lesson, the student will be able to justify different ways of solving addition and subtraction problems by learning about the different strategies of these operations.
A Note for the Teacher
When using strategies to add and subtract, take note of the following:
- Check whether the operation needed is either addition or subtraction.
- Remember that the one place is at the rightmost digit of the number.
- Remind the student that a two-digit number can be decomposed into tens and ones.
- Double-check your final answer.
Theory
- We all know that there is a specific answer derived in an addition or subtraction problem. But, getting the answer does not mean following only one strategy. There are various ways to solve the problem and get the same answer.
Consider the equation, 29 + 42 = ?
- We can solve it vertically:
- Next,
- Lastly,
- We can decompose:
- 29 can be decomposed into 20 + 9
42 can be decomposed into 40 + 2 - Adding the tens together produces 20+40=60
Adding the ones together produces 9+2=11 - 11 can be decomposed into 10+1
- Adding the tens together produces 60+10=70
Adding the two place values together produces 70+1=71 - We can also consider decomposing into words such as:
29 is 2 tens and 9 ones
42 is 4 tens and 2 ones
- 29 can be decomposed into 20 + 9
Consider the equation, 29 + 42 = ?
- We can illustrate:
- 29 can be drawn into
- 42 can be drawn into
- Putting the two illustrations together will produce:
- Counting the model produces 6 tens and 11 ones = 71
- We can use a number line:
Consider the equation, 29 + 42 = ?
- We can solve it vertically:
- Next,
- Lastly,
- We can decompose:
- 30 can be decomposed into 30
19 can be decomposed into 10 & 9 - Subtracting the tens produces 30-10=20
Subtracting the tens and ones produces 20-9=11
- 30 can be decomposed into 30
- We can subtract one from each first:
30-1=29 & 19-1=18
This makes it easier to understand that 29-18=11 - We can use addition:
What value produces 30 when it is added to 19?
19 + ? = 30
Numbers & Operations in Base 10: Strategies to Add & Subtract CCSS 2.NBT.9 Worksheets
This is a fantastic bundle that includes everything you need to know about Numbers & Operations in Base 10: Strategies to Add & Subtract across 23 in-depth pages. These are ready-to-use worksheets that align with the Common Core code 2.NBT.9 for Strategies to Add & Subtract.
Complete List of Included Worksheets
- A lesson plan
- Warm-up activity
- Math theory explained
- Assisted learning activities
- Independent learning activities
- Extension activities and games
- Answer keys
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Link will appear as Numbers & Operations in Base 10: Strategies to Add & Subtract CCSS 2.NBT.9 Worksheets & Activities: https://kidskonnect.com - KidsKonnect, September 3, 2021
Use With Any Curriculum
These worksheets have been specifically designed for use with any international curriculum. You can use these worksheets as-is, or edit them using Google Slides to make them more specific to your own student ability levels and curriculum standards.