Adding Two-Digit Numbers Without Regrouping: Building with Tens and Ones!

Math Grades 1st Grade 1:52 Video
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Lesson Description

Learn how to add two-digit numbers without regrouping by understanding place value and combining tens and ones! We'll use pictures and simple addition to find the answers.

Video Resource

Adding 2-digit numbers without regrouping 1 | Addition and subtraction | 1st grade | Khan Academy

Khan Academy

Duration: 1:52
Watch on YouTube

Key Concepts

  • Place Value (Tens and Ones)
  • Adding Tens
  • Adding Ones

Learning Objectives

  • Students will be able to identify the tens and ones digits in a two-digit number.
  • Students will be able to add two-digit numbers without regrouping using visual aids.
  • Students will be able to explain the process of adding tens and ones separately.

Educator Instructions

  • Introduction (5 mins)
    Begin by reviewing what tens and ones are. Use base-ten blocks or drawings to represent numbers like 23, 45, and 61. Ask students to identify how many tens and ones are in each number. Briefly discuss addition as putting things together.
  • Video Viewing (5 mins)
    Play the Khan Academy video: 'Adding 2-digit numbers without regrouping 1'. Pause at key points (e.g., when Sal introduces the 71 and 24) to ask clarifying questions.
  • Guided Practice (10 mins)
    Work through a few example problems on the board with the students. Use base-ten blocks or drawings to visually represent the addition process. For example, 32 + 15: Represent 32 with 3 tens and 2 ones, and 15 with 1 ten and 5 ones. Combine the tens (3 + 1 = 4 tens) and the ones (2 + 5 = 7 ones). The answer is 47.
  • Independent Practice (10 mins)
    Give students a worksheet with several addition problems involving two-digit numbers without regrouping (e.g., 41 + 26, 53 + 34, 17 + 62). Have them solve the problems using drawings or base-ten blocks. Encourage them to show their work by drawing the tens and ones.
  • Wrap-up (5 mins)
    Review the answers to the independent practice problems. Ask students to explain how they solved one of the problems. Emphasize the importance of adding the ones first, then the tens.

Interactive Exercises

  • Base-Ten Block Addition
    Provide students with base-ten blocks. Call out addition problems (e.g., 23 + 41). Students use the blocks to represent the numbers and combine them to find the sum.
  • Drawing Tens and Ones
    Give students a worksheet with empty boxes labeled 'Tens' and 'Ones'. Call out addition problems. Students draw lines (for tens) and circles (for ones) to represent the numbers and their sum.

Discussion Questions

  • What does the number 35 mean? (3 tens and 5 ones)
  • When we add 2-digit numbers, why do we add the ones and the tens separately?
  • Can you think of a time when you might need to add 2-digit numbers in real life?

Skills Developed

  • Understanding Place Value
  • Addition Skills
  • Problem-Solving

Multiple Choice Questions

Question 1:

What does the number 42 mean?

Correct Answer: 4 tens and 2 ones

Question 2:

What is 20 + 30?

Correct Answer: 50

Question 3:

What is 5 + 4?

Correct Answer: 9

Question 4:

In the number 67, which number is in the ones place?

Correct Answer: 7

Question 5:

If you have 3 tens and 6 ones, what number do you have?

Correct Answer: 36

Question 6:

What is 11 + 1?

Correct Answer: 12

Question 7:

What is 23 + 1?

Correct Answer: 24

Question 8:

What is 10 + 7?

Correct Answer: 17

Question 9:

What is 40 + 5?

Correct Answer: 45

Question 10:

What is 22 + 22?

Correct Answer: 44

Fill in the Blank Questions

Question 1:

The number 56 has ___ tens and 6 ones.

Correct Answer: 5

Question 2:

34 + 2 = ___

Correct Answer: 36

Question 3:

In the number 81, the 8 is in the ___ place.

Correct Answer: tens

Question 4:

When we add 10 + 10 we get ___

Correct Answer: 20

Question 5:

43 + 10 = ___

Correct Answer: 53

Question 6:

7 + 2 = ___

Correct Answer: 9

Question 7:

21 + 6 = ___

Correct Answer: 27

Question 8:

51 + 11 = ___

Correct Answer: 62

Question 9:

3 + 3 = ___

Correct Answer: 6

Question 10:

60 + 4 = ___

Correct Answer: 64

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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