Subtracting Two-Digit Numbers: Tens and Ones!

Math Grades 1st Grade 2:20 Video
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Lesson Description

Learn how to subtract two-digit numbers by understanding tens and ones, just like in the video!

Video Resource

Subtracting two-digit numbers without regrouping (example 2) | 2nd grade | Khan Academy

Khan Academy

Duration: 2:20
Watch on YouTube

Key Concepts

  • Place Value (Tens and Ones)
  • Subtraction
  • Decomposing Numbers

Learning Objectives

  • Students will be able to identify the tens and ones in a two-digit number.
  • Students will be able to subtract two-digit numbers without regrouping by subtracting the ones and then the tens.
  • Students will be able to use visual aids (like drawings of tens and ones) to represent subtraction problems.

Educator Instructions

  • Introduction (5 mins)
    Begin by reviewing the concept of tens and ones. Ask students to identify the tens and ones in various numbers (e.g., What are the tens and ones in 25? What about 43?). Use blocks or drawings to visually represent these numbers.
  • Video Viewing (7 mins)
    Play the Khan Academy video: 'Subtracting two-digit numbers without regrouping (example 2) | 2nd grade | Khan Academy'. Pause the video at key points to ask clarifying questions and ensure understanding.
  • Guided Practice (10 mins)
    Work through a few subtraction problems on the board, using the method shown in the video. Emphasize representing the numbers with drawings of tens and ones. For example, 48 - 23: Draw 4 tens and 8 ones, then cross out 2 tens and 3 ones.
  • Independent Practice (10 mins)
    Give students worksheets with subtraction problems to solve on their own. Encourage them to draw tens and ones to help them visualize the subtraction.
  • Wrap-up (3 mins)
    Review the main concepts of the lesson and answer any remaining questions. Preview what will be covered in the next lesson.

Interactive Exercises

  • Tens and Ones Subtraction Game
    Use online resources or create a class game where students roll dice to create two-digit numbers and then subtract them using base-ten blocks or drawings.
  • Subtraction Story Problems
    Present simple story problems where students need to subtract two-digit numbers. For example: 'Lily has 54 stickers. She gives 21 stickers to her friend. How many stickers does Lily have left?'

Discussion Questions

  • What does the number 32 mean? (3 tens and 2 ones)
  • Why is it important to subtract the ones first and then the tens?
  • Can you think of a time when you use subtraction in your everyday life?

Skills Developed

  • Place Value Understanding
  • Subtraction Skills
  • Problem-Solving

Multiple Choice Questions

Question 1:

What does the 4 in 45 mean?

Correct Answer: 4 tens

Question 2:

What is 6 - 2?

Correct Answer: 4

Question 3:

If you have 3 tens, how many ones do you have?

Correct Answer: 30

Question 4:

What is 57 - 20?

Correct Answer: 37

Question 5:

Which is bigger, 6 tens or 3 tens?

Correct Answer: 6 tens

Question 6:

What is 8 - 5?

Correct Answer: 3

Question 7:

What is the first step when subtracting 2 digit numbers?

Correct Answer: Subtract the ones

Question 8:

Which number is in the tens place in 92?

Correct Answer: 9

Question 9:

What is the number of tens in 40?

Correct Answer: 4

Question 10:

If you have 7 tens and take away 3 tens, how many tens do you have left?

Correct Answer: 4

Fill in the Blank Questions

Question 1:

The number 23 has 2 _____ and 3 ones.

Correct Answer: tens

Question 2:

When you subtract, you are _____ away.

Correct Answer: taking

Question 3:

The number 50 has _____ tens.

Correct Answer: 5

Question 4:

In the number 74, the 4 is in the _____ place.

Correct Answer: ones

Question 5:

46 - 12 = _____.

Correct Answer: 34

Question 6:

The number 37 is made of 3 tens and _____ ones.

Correct Answer: 7

Question 7:

If you have 6 tens and take away 2 tens, you have _____ tens left.

Correct Answer: 4

Question 8:

When subtracting two-digit numbers, subtract the _____ place first.

Correct Answer: ones

Question 9:

78 - 30 = _____.

Correct Answer: 48

Question 10:

The opposite of subtraction is _____

Correct Answer: addition

Educational Standards

1.NBT.C.6:Subtract multiples of 10 in the range 10-90 from multiples of 10 in the range 10-90 (positive or zero differences), 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. 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

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