Finding Unknown Numbers in Addition and Subtraction
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Subject Area: English Language Arts (B.E.S.T.) | Grade Level: 2
Lesson Length: 45 minutes
Keywords/Tags: Addition, Subtraction, Unknown Numbers
Lesson Description: In this lesson, we'll use related equations to determine the unknown whole number in an addition or subtraction equation. Students will watch the video, complete questions, and navigate resources.

  • MA.2.AR.2.2 Determine the unknown whole number in an addition or subtraction equation, relating three or four whole numbers, with the unknown in any position.
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Video : Finding the unknown number - 1st Grade Math (1.OA.8)
Instructions: Please watch the following video as many times as needed before starting to go through other lesson pages. Understanding the content of the video is very important since the lesson activities will be all about this video content.
Description: In this lesson, we'll use related equations to determine the unknown whole number in an addition or subtraction equation.
Quiz : Finding Unknown Number in Addition and Subtraction Equations
Instructions: Please complete this quiz by choosing the correct answer for each question. You can take this quiz as many times as needed. Use math methods demonstrated in the video to find the unknown number for each item.
Question #1

3+X=9

Question #2

8+X=12

Question #3

X-5=5

Question #4

12-X=7

Question #5
5+X=9, X=5
Question #6
X-7=3, X=10 
Question #7
X-6=2
Question #8
7+X=13
Question #9
9+X=14
Question #10
5-2=X
Description: 10 addition and subtraction equation questions.
Resources : Extra fun practice tools!
Instructions: Please see additional external resources below. Feel free visit each link to learn more about this lesson.
Practice Game to find Unknown Variables in Addition
Game to practice unknown variables in addition.
Practice Game to find Unknown Variables in Subtraction
A practice game to find unknown variables in subtraction
Subtraction with Unknown Addends 1st Grade Math Videos for Kids
Animated video set in space!
Description: Here are some websites that will help practice this topic!