Missing Number Mania: Unlocking Addition Secrets!

Mathematics Grades 3rd Grade 5:36 Video
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Lesson Description

Learn how to find the missing number in addition problems using fact families and subtraction! Become a math detective and crack the code!

Video Resource

How to Add Unknown Numbers

Miacademy Learning Channel

Duration: 5:36
Watch on YouTube

Key Concepts

  • Fact Families
  • Inverse Relationship (Addition and Subtraction)
  • Finding Unknowns in Addition Equations

Learning Objectives

  • Students will be able to identify and explain the relationship between addition and subtraction.
  • Students will be able to use subtraction to find the missing number in an addition problem.
  • Students will be able to solve addition problems with unknowns, including problems that require regrouping (borrowing).

Educator Instructions

  • Introduction (5 mins)
    Begin by reviewing the concept of addition and fact families. Ask students to give examples of fact families they know. Introduce the idea that sometimes one number in an addition problem is missing, and we need to find it.
  • Video Viewing (7 mins)
    Watch the Miacademy Learning Channel video 'How to Add Unknown Numbers'. Encourage students to pay attention to how Ashley uses fact families and subtraction to find the missing number.
  • Guided Practice (10 mins)
    Work through several example problems together on the board, similar to those in the video. Start with simple problems (e.g., 5 + ? = 8) and gradually increase the difficulty, including problems that require borrowing (regrouping) in subtraction (e.g., 28 + ? = 40).
  • Independent Practice (10 mins)
    Provide students with a worksheet containing various addition problems with unknowns. Encourage them to use the subtraction strategy they learned in the video. Circulate to provide support and answer questions.
  • Wrap-up (3 mins)
    Review the key concepts of the lesson. Ask students to explain in their own words how to find the missing number in an addition problem. Briefly discuss the importance of checking their answers.

Interactive Exercises

  • Number Bond Activity
    Provide students with number bond templates. Fill in the total and one of the parts, and have students find the missing part using subtraction.
  • Equation Scramble
    Write addition equations with unknowns on separate slips of paper. Scramble the numbers and symbols. Students must rearrange the slips to create a correct equation.

Discussion Questions

  • What is a fact family, and how can it help us with addition and subtraction?
  • How does subtraction help us find the missing number in an addition problem?
  • What do we need to do if the subtraction problem requires borrowing (regrouping)?

Skills Developed

  • Addition Fluency
  • Subtraction Fluency
  • Problem-Solving
  • Critical Thinking
  • Understanding Number Relationships

Multiple Choice Questions

Question 1:

What is a fact family?

Correct Answer: A group of related addition and subtraction facts.

Question 2:

To find the missing number in 7 + ? = 10, what should you do?

Correct Answer: Subtract 7 from 10.

Question 3:

What is the missing number in 4 + ? = 9?

Correct Answer: 5

Question 4:

What is the missing number in 15 + ? = 20?

Correct Answer: 5

Question 5:

What is the missing number in 20 + ? = 35?

Correct Answer: 15

Question 6:

What is the missing number in 12 + ? = 18?

Correct Answer: 6

Question 7:

What is the missing number in 11 + ? = 21?

Correct Answer: 10

Question 8:

What is the missing number in 3 + ? = 6?

Correct Answer: 3

Question 9:

What is the missing number in 19 + ? = 20?

Correct Answer: 1

Question 10:

What is the missing number in 50 + ? = 100?

Correct Answer: 50

Fill in the Blank Questions

Question 1:

In the problem 6 + ____ = 10, the missing number is ____.

Correct Answer: 4

Question 2:

To find the missing number, you can ____ the number you know from the total.

Correct Answer: subtract

Question 3:

A fact family includes related ____ and ____ facts.

Correct Answer: addition, subtraction

Question 4:

If 8 + ____ = 12, then 12 - 8 = ____.

Correct Answer: 4, 4

Question 5:

If ? + 3 = 7, then 7 - 3 = ____.

Correct Answer: 4

Question 6:

If 23 + ____ = 30, then the missing number is ____.

Correct Answer: 7

Question 7:

If 10 + ____ = 100, then the missing number is ____.

Correct Answer: 90

Question 8:

If ____ + 5 = 15, then the missing number is ____.

Correct Answer: 10

Question 9:

If 22 + ____ = 25, then the missing number is ____.

Correct Answer: 3

Question 10:

If 3 + ____ = 12, then the missing number is ____.

Correct Answer: 9

Educational Standards

3.A.2.1:Use number sense with the properties of addition, subtraction, and multiplication, to find unknowns (represented by symbols) in one-step equations. Generate real-world situations to represent number sentences. 3.N.2.3:Use strategies and algorithms based on knowledge of place value and equality to fluently add and subtract up to five-digit numbers (answer not to exceed 100,000). 3.N.2.5:Use addition and subtraction to solve problems involving whole numbers. Use various strategies, including the relationship between addition and subtraction and the context of the problem to assess the reasonableness of results.

Teaching Materials

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