Adding Two-Digit Numbers: Let's Build and Add!

Math Grades 1st Grade 2:33 Video
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Lesson Description

Learn how to add two-digit numbers by understanding place value. We'll use blocks to represent tens and ones, then add them together! (No regrouping)

Video Resource

Adding two-digit numbers without regrouping | Early Math | Khan Academy

Khan Academy

Duration: 2:33
Watch on YouTube

Key Concepts

  • Place Value (Tens and Ones)
  • Adding Tens and Ones Separately
  • Two-Digit Addition (without regrouping)

Learning Objectives

  • Students will be able to identify the tens and ones digits in a two-digit number.
  • Students will be able to add the ones digits of two two-digit numbers.
  • Students will be able to add the tens digits of two two-digit numbers.
  • Students will be able to add two-digit numbers without regrouping.

Educator Instructions

  • Introduction (5 mins)
    Begin by reviewing place value. Ask students what the numbers in 23 and 45 mean (2 tens and 3 ones, 4 tens and 5 ones). Use physical manipulatives like base-ten blocks to visualize this.
  • Video Viewing (7 mins)
    Show the Khan Academy video 'Adding two-digit numbers without regrouping'. Pause at key moments to ask students questions about what they are seeing.
  • Guided Practice (10 mins)
    Work through a few more examples on the board. Emphasize lining up the ones and tens digits. Use different colors for the ones and tens columns to help students visually separate them. Examples: 12 + 34, 25 + 52, 61 + 18.
  • Independent Practice (10 mins)
    Give students a worksheet with several two-digit addition problems without regrouping. Have them show their work by drawing base-ten blocks or writing out the tens and ones. Provide assistance as needed.
  • Wrap-up (3 mins)
    Review the key concepts of the lesson. Ask students to explain in their own words how to add two-digit numbers without regrouping.

Interactive Exercises

  • Base-Ten Block Addition
    Provide students with base-ten blocks. Call out addition problems (e.g., 21 + 35). Have students build each number with the blocks, then combine the blocks to find the sum.
  • Place Value Chart Addition
    Provide students with a place value chart (tens and ones columns). Write addition problems. Have students write each number in the chart, then add the columns to find the sum.

Discussion Questions

  • What is place value? Why is it important?
  • How are tens and ones different?
  • When we add two-digit numbers, why do we add the ones first?
  • Can you think of a real-life situation where you might need to add two-digit numbers?

Skills Developed

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

Multiple Choice Questions

Question 1:

What does the 2 in 25 stand for?

Correct Answer: 2 tens

Question 2:

What is 14 + 2?

Correct Answer: 16

Question 3:

What is 30 + 10?

Correct Answer: 40

Question 4:

What is 5 + 3?

Correct Answer: 8

Question 5:

What is the ones place in 45?

Correct Answer: 5

Question 6:

What is the tens place in 62?

Correct Answer: 6

Question 7:

What is 11 + 11?

Correct Answer: 22

Question 8:

Which number has 3 tens and 7 ones?

Correct Answer: 37

Question 9:

We add ____ and ____ when we are adding tens and ones.

Correct Answer: ones, tens

Question 10:

Which of these equals to 8?

Correct Answer: 4 + 4

Fill in the Blank Questions

Question 1:

In the number 32, the 3 is in the ____ place.

Correct Answer: tens

Question 2:

In the number 17, the 7 is in the ____ place.

Correct Answer: ones

Question 3:

20 + 10 = ____

Correct Answer: 30

Question 4:

4 + 5 = ____

Correct Answer: 9

Question 5:

To add 2-digit numbers, we add the ones and the ____ separately.

Correct Answer: tens

Question 6:

13 + 1 = ____

Correct Answer: 14

Question 7:

The number 40 has ____ tens.

Correct Answer: four

Question 8:

____ + 5 = 10

Correct Answer: 5

Question 9:

If I have 2 tens and 6 ones, I have ____.

Correct Answer: 26

Question 10:

3 + 4 = ____

Correct Answer: 7

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: 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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