Subtracting Numbers From Themselves: Always Zero!

Math Grades 1st Grade 5:01 Video
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Lesson Description

Learn the super cool math fact: when you subtract a number from itself, the answer is always zero! Join us for a fun lesson.

Video Resource

Grade 1: Math Lesson # 62b Subtraction Facts: Subtracting A Number From Itself

The Eagle's Nest - Our Online Classroom

Duration: 5:01
Watch on YouTube

Key Concepts

  • Subtraction
  • Zero
  • Number Sense

Learning Objectives

  • Students will be able to subtract a number from itself.
  • Students will understand that the answer when subtracting a number from itself is always zero.

Educator Instructions

  • Introduction (5 mins)
    Begin by asking students if they know what happens when you take away all of something. Introduce the concept of zero. Explain that today we're learning about a special subtraction rule: when you subtract a number from itself, the answer is always zero.
  • Watch the Video (5 mins)
    Play the YouTube video: 'Grade 1: Math Lesson # 62b Subtraction Facts: Subtracting A Number From Itself'. Encourage students to pay attention to the examples.
  • Practice Examples (10 mins)
    Work through several examples on the board. Start with simple numbers like 1-1, 2-2, 3-3, and then move to slightly larger numbers if the students understand (e.g., 7-7, 9-9). Use manipulatives like blocks or counters to visually demonstrate the concept. For example, if you have 5 blocks and you take away 5 blocks, you have 0 blocks left.
  • Word Problems (5 mins)
    Present simple word problems: 'I had 3 apples and I ate 3 apples. How many apples do I have left?' 'There were 8 birds on a tree, and 8 birds flew away. How many birds are left?'
  • Wrap-up (5 mins)
    Review the main concept: any number minus itself equals zero. Ask students to give their own examples.

Interactive Exercises

  • Draw and Subtract
    Have students draw a picture of a set of objects (e.g., 6 stars). Then, have them cross out the same number of objects (e.g., cross out all 6 stars). Ask them how many are left (0).

Discussion Questions

  • What happens when you have some toys, and then you give them all away?
  • Can you think of a time when you subtracted something from itself?

Skills Developed

  • Subtraction
  • Problem-solving
  • Number recognition

Multiple Choice Questions

Question 1:

What is 5 - 5?

Correct Answer: 0

Question 2:

What is 9 - 9?

Correct Answer: 0

Question 3:

What is 2 - 2?

Correct Answer: 0

Question 4:

If you have 4 cookies and you eat 4 cookies, how many cookies do you have left?

Correct Answer: 0

Question 5:

What is 7 - 7?

Correct Answer: 0

Question 6:

What does 'subtract' mean?

Correct Answer: Take away

Question 7:

What number do you get when you subtract a number from itself?

Correct Answer: Zero

Question 8:

If there are 3 birds and all three fly away, how many are left?

Correct Answer: 0

Question 9:

What is 1 - 1?

Correct Answer: 0

Question 10:

If you have 6 pencils and you give away 6 pencils, how many pencils do you have left?

Correct Answer: 0

Fill in the Blank Questions

Question 1:

3 - 3 = ____

Correct Answer: 0

Question 2:

8 - 8 = ____

Correct Answer: 0

Question 3:

10 - 10 = ____

Correct Answer: 0

Question 4:

6 - ____ = 0

Correct Answer: 6

Question 5:

____ - 4 = 0

Correct Answer: 4

Question 6:

When you subtract a number from ____, the answer is always zero.

Correct Answer: itself

Question 7:

5 - 5 is the same as ____.

Correct Answer: 0

Question 8:

7 minus 7 equals ____.

Correct Answer: 0

Question 9:

2 - ____ = 0

Correct Answer: 2

Question 10:

A number minus itself equals ____.

Correct Answer: zero

Educational Standards

CCSS.Math.Content.1.OA.C.6:Add and subtract within 20, demonstrating fluency for addition and subtraction within 10. CCSS.Math.Content.1.OA.B.4:Understand subtraction as an unknown-addend problem. For example, subtract 10 - 8 by finding the number that makes 10 when added to 8. 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.

Teaching Materials

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