Regrouping: Let's Break Down Numbers!

Math Grades 1st Grade 4:42 Video
Print Lesson Plan Watch Video

Lesson Description

Learn how to regroup tens and ones to make subtraction easier, just like in the Khan Academy video!

Video Resource

Visual understanding of regrouping

Khan Academy

Duration: 4:42
Watch on YouTube

Key Concepts

  • Place Value (Tens and Ones)
  • Regrouping (Borrowing)
  • Subtraction with Regrouping

Learning Objectives

  • Students will be able to identify the tens and ones in a two-digit number.
  • Students will be able to explain the concept of regrouping (borrowing) in subtraction.
  • Students will be able to subtract two-digit numbers with regrouping using visual aids and strategies learned.

Educator Instructions

  • Introduction (5 mins)
    Begin by reviewing place value. Ask students what each digit represents in numbers like 23, 47, and 61. Use physical manipulatives like base-ten blocks if available. Explain that sometimes, when we subtract, we need to 'borrow' from the tens place to help us subtract the ones.
  • Video Viewing (7 mins)
    Watch the Khan Academy video: 'Visual understanding of regrouping' (https://www.youtube.com/watch?v=AxwkJtvVaZk). Pause at key points to explain what is happening on the screen and answer any questions.
  • Guided Practice (10 mins)
    Work through a few subtraction problems together as a class, using base-ten blocks or drawings to visually represent the regrouping process. For example, 42 - 15. Emphasize that we can't take 5 from 2, so we borrow a ten.
  • Independent Practice (10 mins)
    Students work independently on a worksheet with subtraction problems that require regrouping. Provide support as needed. Encourage students to use drawings or base-ten blocks to help them.
  • Wrap-up (3 mins)
    Review the key concepts of regrouping. Ask students to explain in their own words how and why we regroup in subtraction. Review answers to the independent practice problems.

Interactive Exercises

  • Base-Ten Block Subtraction
    Provide each student with base-ten blocks (or drawings of base-ten blocks). Give them subtraction problems and have them physically manipulate the blocks to perform the regrouping and subtraction.
  • Number Line Subtraction
    Use a number line to visually demonstrate subtraction with regrouping. For example, to solve 31 - 14, start at 31, break 14 into 10 and 4, and jump back 10, then jump back 4, regrouping as needed on the number line. This helps them visualize the breaking down of the numbers.

Discussion Questions

  • What does it mean to 'regroup' in subtraction?
  • Why do we need to regroup sometimes when we subtract?
  • Can you give me an example of when you would need to regroup?

Skills Developed

  • Place Value Understanding
  • Subtraction Skills
  • Problem-Solving
  • Visual Representation

Multiple Choice Questions

Question 1:

What does it mean to regroup in subtraction?

Correct Answer: To borrow from the tens place

Question 2:

In the number 35, how many TENS are there?

Correct Answer: 3

Question 3:

In the number 72, how many ONES are there?

Correct Answer: 2

Question 4:

Why do we sometimes need to regroup?

Correct Answer: To make subtraction easier

Question 5:

If you have 42 - 17, do you need to regroup?

Correct Answer: Yes

Question 6:

What happens to the tens place when you regroup?

Correct Answer: It gets smaller

Question 7:

Which of these is a ten?

Correct Answer: 10

Question 8:

Which place do we look at FIRST when we subtract?

Correct Answer: The ones place

Question 9:

If you borrow 1 ten, how many ones do you get?

Correct Answer: 10

Question 10:

What is 58 - 20?

Correct Answer: 38

Fill in the Blank Questions

Question 1:

When we subtract, we start with the ______ place.

Correct Answer: ones

Question 2:

Regrouping is also called ________.

Correct Answer: borrowing

Question 3:

In the number 63, the 6 is in the _______ place.

Correct Answer: tens

Question 4:

When we regroup, we take a ten and turn it into ______ ones.

Correct Answer: 10

Question 5:

If you have 32 - 15, you need to ________.

Correct Answer: regroup

Question 6:

The number 40 has ____ tens and 0 ones.

Correct Answer: 4

Question 7:

When we regroup, the tens place gets ________.

Correct Answer: smaller

Question 8:

Subtracting means to _______.

Correct Answer: take away

Question 9:

10 ones is the same as ____ ten.

Correct Answer: 1

Question 10:

When you regroup in 64-28, you change 6 tens to __ tens.

Correct Answer: 5

Educational Standards

1.NBT.C.4:Add within 100, including adding a two-digit number and a one-digit number, and adding a two-digit number and a multiple of 10, using concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship between addition and subtraction; relate the strategy to a written method and explain the reasoning used. Understand that in adding two-digit numbers, one adds tens and tens, ones and ones; and sometimes it is necessary to compose a ten. 1.NBT.B.2:Understand that the two digits of a two-digit number represent amounts of tens and ones. Understand the following as special cases: 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

Download ready-to-use materials for this lesson:

Student Worksheet Classroom Slides Assessment Quiz Export to Google Docs
Add to Google Classroom

User Actions

Sign in to save this lesson plan to your favorites.

Sign In

Share This Lesson

Related Lesson Plans