Half It! Subtracting Half of a Number

Math Grades 1st Grade 4:41 Video
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Lesson Description

Learn how to subtract half of even numbers using fun counting tools! This lesson helps you understand what it means to divide numbers in half and take away one half.

Video Resource

Grade 1: Math Lesson #68 Subtracting Half Of A Number

The Eagle's Nest - Our Online Classroom

Duration: 4:41
Watch on YouTube

Key Concepts

  • Even numbers
  • Halving (dividing into two equal parts)
  • Subtraction

Learning Objectives

  • Students will be able to identify even numbers up to 20.
  • Students will be able to subtract half of even numbers up to 20.
  • Students will be able to explain the concept of 'half' in relation to even numbers.

Educator Instructions

  • Introduction (5 mins)
    Begin by asking students what they already know about the word 'half'. Use real-life examples, such as cutting a cookie in half. Introduce the concept that this lesson will focus on finding half of numbers.
  • Video Viewing (7 mins)
    Play the video 'Grade 1: Math Lesson #68 Subtracting Half Of A Number'. Encourage students to follow along with linking cubes or other counting objects as demonstrated in the video.
  • Guided Practice (10 mins)
    Work through examples similar to those in the video, such as subtracting half of 4, 6, and 8. Use manipulatives like linking cubes, LEGOs, or drawings to help students visualize the process. Emphasize that they are splitting the group into two equal parts and taking one part away.
  • Independent Practice (8 mins)
    Provide students with a worksheet or have them work independently with manipulatives to solve problems like: What is half of 10? What is half of 12? What is half of 14? Ask them to show their work with drawings or cubes.
  • Wrap-up (5 mins)
    Review the key concept of finding half of an even number. Ask students to explain in their own words how they would find half of a number. Reiterate that when subtracting half of a number, you are dividing it into two equal groups and taking one group away.

Interactive Exercises

  • Linking Cube Challenge
    Give each student a number of linking cubes (an even number less than 20). Ask them to divide the cubes into two equal groups. Then, have them subtract one of the groups. Ask: How many cubes did you start with? How many did you subtract? How many are left?
  • Drawing Halves
    Provide students with sheets of paper containing pictures of even numbers of objects (e.g., 6 apples, 8 stars). Have them circle half of the objects and write a subtraction equation to match (e.g., 6 - 3 = 3).

Discussion Questions

  • What does it mean to cut something in half?
  • How can you make sure you have two equal groups when dividing in half?

Skills Developed

  • Subtraction
  • Problem-solving
  • Visualizing math concepts

Multiple Choice Questions

Question 1:

What is half of 4?

Correct Answer: 2

Question 2:

What is half of 10?

Correct Answer: 5

Question 3:

If you have 6 cookies and give half away, how many cookies do you give away?

Correct Answer: 3

Question 4:

What is half of 8?

Correct Answer: 4

Question 5:

What is half of 12?

Correct Answer: 6

Question 6:

Which of these numbers is an even number?

Correct Answer: 2

Question 7:

What do you need to do to a number to find 'half' of it?

Correct Answer: Take half away

Question 8:

If you have 14 toys and give half away, how many do you have left?

Correct Answer: 7

Question 9:

What is half of 16?

Correct Answer: 8

Question 10:

If you have 20 stickers and give half away, how many did you give away?

Correct Answer: 10

Fill in the Blank Questions

Question 1:

Half of 2 is ______.

Correct Answer: 1

Question 2:

Half of 6 is ______.

Correct Answer: 3

Question 3:

Half of 18 is ______.

Correct Answer: 9

Question 4:

Half of 14 is ______.

Correct Answer: 7

Question 5:

Half of 20 is ______.

Correct Answer: 10

Question 6:

When you find half of a number, you split it into _____ equal parts.

Correct Answer: 2

Question 7:

To find half, you _________ part of the number away.

Correct Answer: subtract

Question 8:

Half of 12 is ______.

Correct Answer: 6

Question 9:

Half of 8 is ______.

Correct Answer: 4

Question 10:

Half of 10 is ______.

Correct Answer: 5

Educational Standards

CCSS.Math.Content.1.OA.C.6:Add and subtract within 20, demonstrating fluency for addition and subtraction within 10. Use strategies such as counting on; making ten (e.g., 8 + 6 = 8 + 2 + 4 = 10 + 4 = 14); decomposing a number leading to a ten (e.g., 13 - 4 = 13 - 3 - 1 = 10 - 1 = 9); using the relationship between addition and subtraction (e.g., knowing that 8 + 4 = 12, one knows 12 - 8 = 4); and creating equivalent but easier or known sums (e.g., adding 6 + 7 by creating the known equivalent 6 + 6 + 1 = 12 + 1 = 13). 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.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.

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