Number Machine Fun: Adding and Subtracting to Find Missing Numbers

Math Grades 1st Grade 9:55 Video
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Lesson Description

Let's learn how to find missing numbers in math problems using number machines! We'll practice adding and subtracting, and use the 'associative property' to help us solve tricky equations.

Video Resource

Addition and Subtraction Practice - 1st Grade | Math | Kids Academy

Kids Academy

Duration: 9:55
Watch on YouTube

Key Concepts

  • Addition and Subtraction
  • Unknown Numbers
  • Associative Property (rearranging equations)

Learning Objectives

  • Students will be able to identify missing numbers in addition and subtraction equations.
  • Students will be able to use addition and subtraction to find the missing number.
  • Students will be able to apply the concept of the associative property to solve for missing numbers.

Educator Instructions

  • Introduction (5 mins)
    Begin by asking students what they know about addition and subtraction. Introduce the idea of a 'number machine' - a machine where you put in a number, it does something to it (adds or subtracts), and then a new number comes out.
  • Video Viewing (7 mins)
    Watch the Kids Academy video 'Addition and Subtraction Practice - 1st Grade'. Pay attention to how the video explains finding the rule (addition or subtraction) and how it finds the missing numbers.
  • Guided Practice (10 mins)
    Work through examples similar to those in the video, writing them on the board. Start with simpler problems, like 5 + ? = 8 or 10 - ? = 3. Then, progress to problems where the unknown is at the beginning, such as ? - 2 = 6. Emphasize using fingers, drawing, or objects to visualize the math.
  • Associative Property Explanation (5 mins)
    Explain that we can sometimes move numbers around to help us solve problems. Use a simple example: If ? - 1 = 4, then 1 + 4 = ? to help them understand the concept. Call it the 'Switcheroo' strategy to make it fun.
  • Independent Practice (8 mins)
    Provide students with a worksheet or use online interactive exercises where they can practice finding missing numbers. Encourage them to use the 'Switcheroo' strategy when needed.
  • Wrap-up (5 mins)
    Review the main concepts of the lesson. Ask students what they learned and how they can use these skills in everyday life.

Interactive Exercises

  • Number Machine Game
    Create a simple 'Number Machine' game on the board. Write a rule (+2, -1, etc.) and have students take turns guessing the output when you give them an input, or vice versa.
  • Missing Number Worksheet
    Prepare a worksheet with a variety of addition and subtraction problems with missing numbers in different positions. Students should fill in the blanks to complete the equations.

Discussion Questions

  • What happens to a number when you add to it? Does it get bigger or smaller?
  • What happens to a number when you subtract from it? Does it get bigger or smaller?
  • Can you think of a time when you needed to find a missing number in real life?

Skills Developed

  • Addition and Subtraction Fluency
  • Problem-Solving
  • Logical Reasoning

Multiple Choice Questions

Question 1:

What does it mean to add?

Correct Answer: To put together

Question 2:

What does it mean to subtract?

Correct Answer: To take away

Question 3:

What is 5 + 2?

Correct Answer: 7

Question 4:

What is 10 - 3?

Correct Answer: 7

Question 5:

In the problem 3 + ? = 5, what number is missing?

Correct Answer: 2

Question 6:

In the problem ? - 2 = 4, what number is missing?

Correct Answer: 8

Question 7:

Which sign means to add?

Correct Answer: +

Question 8:

Which sign means to subtract?

Correct Answer: -

Question 9:

If you have 4 cookies and get 3 more, how many cookies do you have?

Correct Answer: 7

Question 10:

If you have 8 balloons and 2 pop, how many balloons are left?

Correct Answer: 6

Fill in the Blank Questions

Question 1:

Adding means to put numbers ___________.

Correct Answer: together

Question 2:

Subtracting means to __________ numbers.

Correct Answer: take away

Question 3:

5 + 3 = __________

Correct Answer: 8

Question 4:

10 - 4 = __________

Correct Answer: 6

Question 5:

2 + _____ = 6

Correct Answer: 4

Question 6:

_____ - 1 = 7

Correct Answer: 8

Question 7:

The sign that means to add is _________.

Correct Answer: +

Question 8:

The sign that means to subtract is _________.

Correct Answer: -

Question 9:

7 + 2 more is ___________

Correct Answer: 9

Question 10:

10 take away 5 is ___________

Correct Answer: 5

Educational Standards

CCSS.Math.Content.1.OA.A.1:Use addition and subtraction within 20 to solve word problems involving situations of adding to, taking from, putting together, taking apart, and comparing, with unknowns in all positions, e.g., by using objects, drawings, and equations with a symbol for the unknown number to represent the problem. CCSS.Math.Content.1.OA.D.8:Determine the unknown whole number in an addition or subtraction equation relating three whole numbers. For example, determine the unknown number that makes the equation true in each of the equations 8 + ? = 11, 5 = _ - 3, 6 + 6 = _. CCSS.Math.Content.1.OA.B.3:Apply properties of operations as strategies to add and subtract. (Students need not use formal terms for these properties.) Examples: If 8 + 3 = 11 is known, then 3 + 8 = 11 is also known. (Commutative property of addition.) To add 2 + 6 + 4, the second two numbers can be added to make a ten, so 2 + 6 + 4 = 2 + 10 = 12. (Associative property of addition.)

Teaching Materials

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