Addition of 2 Digit Numbers

Week 3

Learning Outcome

Performs addition of 2-digit numbers fluently using flexible strategies.

Objective

Children will be able to use different strategies to show and solve addition problems involving two-digit numbers, with and without regrouping, using the number line and procedural method.

Prerequisites

Children can perform single-digit addition.

Pre-teach Vocabulary

Children should be familiar with the terms such as, place value, add, plus and equal to.

Introduction: Strategies to Solve Subtraction Problems

The teacher could begin the class by saying, ‘today we are going to learn two different strategies to solve addition problems with two-digit numbers.’

We will use:

  • A number line to jump forward.
  • The step-by-step column method (procedural method).

And then ask,

  • When would we need to regroup in addition?

Materials required:

  1. Whiteboard/Chart paper
  2. Number line strips (individual and large display)
  3. Base-ten blocks (optional for concrete practice)
  4. Pencils and erasers
  5. Addition worksheets (with mixed regrouping and non-regrouping problems)
  6. Math notebooks

Teaching Method: I Do – We Do – You Do

I DO (Teacher Modeling):

Number Line Strategy
Model with: 47 + 23 = ?

  • Start at 47 on the number line.
  • Hop forward 20 (two jumps of 10).
  • Hop forward 3 more.
  • End at 70.
  • Say: 47 plus 23 equals 70. I used big jumps for Tens, and small jumps for ones.

Procedural (Column) Method – No Regrouping

Model: 54 + 21= ?
   54
+ 21
______
  75

  • Add ones: 4 + 1 = 5
  • Add tens:  5 + 2 = 7

Procedural (Column) Method with Regrouping 
Example: 56 + 38

Step 1: Write the problem in vertical form.

  • Add the Ones Place first. It is 14.
  • 14 is greater than 10.
  • So, we need to regroup.

Step 2: Regroup a Ten

  • We regroup 1 ten from the ones place in the total.
  • That leaves 4 ones and 1 ten is taken to tens column.
  • Add the Tens column. We get 9

Now the problem looks like this:

Step 3: Add Ones and Tens

  • 4 (ones place)
  • 9  (tens place)

Final Answer: 94

We Do (Guided Practice):

Let the children work with the teacher’s guidance.

Number Line
Problem: 63 + 25 =?

  • Ask: Where do we start on the number line?
  • Answer: 63
  • Help the children to count forward: 2 jumps of 10 and then take 5 jumps of 1.
  • You land on 88. So, the answer is 63 + 25 = 88

Procedural Method

Problem: 47 + 16 =?

Write the problem in vertical form:
47
+16
_____
?
______

Ask guiding questions to involve the children:

  • What number do you get if you add the ones column?
  • Answer: 13.
  • Is 13 greater than 10? Yes.
  • What do I do now?
  • I regroup by taking 10 ones and replacing it to one ten. 
  • Explain and model regrouping.
  • After regrouping I have 3 ones in the Ones column and one more Ten in the tens column. 
  • Add Tens column. I get 6 Tens.
  • So, the answer is 63.

Solve step by step with the children.

You Do (Independent Practice):

Provide 6 mixed problems:

  • 3 without regrouping
  • 3 with regrouping

Children will solve:

  • 3 using number line (drawn or paper strip)
  • 3 using procedural method

Video: Strategies to solve addition problems – Coming soon

ISL Video: Strategies to solve addition problems – Coming soon

LTM: DIY Flashcards – Coming soon

LTM: Printable Flashcards – Coming soon

Activity 1: Jigsaw Puzzle to Identify the Image

Objective: 
To find the total sum of two, 2-digit numbers by grouping or regrouping and solving the puzzle to get the hidden image.

Importance of the activity for children:

Helps in developing:

  1. Fine motor skills (Holding the piece of board, hand-eye coordination)
  2. Cognitive skills (Concentration, problem-solving,)
  3. Social skills (Cooperation, waiting for their turn, playing together)
  4. Language skills (Articulating, concepts formation like ‘addition, regrouping’)
  5. Emotional skills (Builds confidence in numeracy, promotes a sense of achievement that boosts self-esteem, and encourages pride in learning new skills)

Resources required:

  • Jigsaw puzzle cardboard pieces with the question on one set of cardboard pieces (10)
  • Cardboard pieces with the answer printed on the picture. (10)

Setting for the activity:
The activity can be done indoors or outdoors depending on the space availability. 

Type of activity: Group activity

Preparation of activity:
The teacher will make sure the set of pieces is ready. 

Role of the teacher: Demonstrator, observer, and facilitator.

Preparation of the puzzle:

  1. First the jigsaw puzzle of 10 cardboard pieces are made with the addition sum. In another set of cardboard pieces, answers are written /printed.
  2. Make them into one full pack with question pieces and answer pieces.

Procedure:

  1. The class is divided into groups of 4 children.
  2. Each group will get a pack of two sets of puzzles, one with a question and the other one set with the answer printed on a part of a picture.
  3. The group will solve the puzzle by finding the answer for the addition (using different strategies), arranging the answers in the written way of questions, and identifying the hidden picture.

Observations:
The teacher observes the children engaged in the activity to find:

  1. Are the children able to solve the two-digit addition problems using appropriate strategies such as regrouping, number line, or column method?
  2. Are they able to demonstrate understanding of the addition concept by correctly matching the question pieces with the corresponding answer pieces?

Suggested Variations:
The teacher can incorporate visuals and props to make the lesson more engaging.

Conclusion:
Children would be able to solve subtraction problems creatively using the manipulatives.

LTM: Puzzles – Coming soon

Activity 2: Crossword Puzzle

Objective: 
To apply the concept of addition to solve the crossword puzzle.

Importance of the activity for children:

Helps in developing:

  1. Gross motor skills (Sitting erect, bending)
  2. Fine motor skills (Writing, holding a pencil)
  3. Cognitive skills (Solving the puzzle, associating facts, filling the number name of the answer)
  4. Social skills (Cooperation, waiting for their turn, discussing)
  5. Emotional skills (Builds confidence in numeracy, promotes a sense of achievement that boosts self-esteem, and encourages pride in learning new skills) 

Resources required:
A4 sheet with the crossword puzzle.

Setting for the activity: 
The activity can be done indoors or outdoors depending on the space availability. 

Type of activity: Group activity

Preparation of activity:
The teacher will make sure about the availability of resources. 

Role of the teacher: Demonstrator, observer, and facilitator.

Procedure:

  1. The class will be divided into groups of 3 children.
  2. Each group will get a puzzle sheet. They have to solve the addition sums and fill up the puzzle sheet using the clues given. 

Observation:
The teacher observes the children engaged in the activity to find:

  1. Are children able to solve addition problems correctly using appropriate strategies?
  2. Can they convert numerical answers into number names correctly?

Suggested Variations:

  1. The teacher can start the activity by demonstrating with different numbers.
  2. The difficulty level can be increased by increasing the number.

Conclusion:
Children would learn to subtract two-digit numbers using different strategies.

LTM: Crossword puzzle – Coming soon

Assessment

The teacher can give the practice worksheet to the children which can be followed by an assessment worksheet.

Worksheet: Practice worksheet- Coming soon

Worksheet: Practice worksheet (Enlarged) – Coming soon

Worksheet: Assessment worksheet – Coming soon

Worksheet: Assessment worksheet (Enlarged) – Coming soon

Cross-Curricular Connection:

  • Art Class:
    • The addition problem can be presented in pictorial form, and the children can be asked to give the answers in picture form. For example, 15 stars (picture form) +12 stars (picture form) =? Answer: the child should draw 27 stars.
    • From picture cutouts kept in a box, the children can be asked to pick similar pictures, form a problem, find a solution, and paste it on a sheet. Example, Pick 15 flowers and again 11 flowers, form a problem, 15 +11=? Pick 26 flowers and paste the pictures in the sheet and show the answer as 26. 
    • Children can cut out similar pictures themselves, create a problem, find a solution, and paste everything on a sheet.
  • Human values Class:
    • The concept of adding (performing) good deeds every day to become a better person can be integrated into Human Values class lessons
  • Language Class:
    Children can be encouraged to talk about the concept of addition through real- life examples in the class. For example, a child can narrate a story like this: I bought a few vegetables for ₹ 52 and fruits for ₹ 40. So, in total I have spent ₹92.
  • I travel 12 km one way to reach school every day. So in total, I travel 12 +12 =24 km every day.

Check list for teacher:

ActivityYesNoSometimes
Children can:
Understand the addition problems and the rules to solve them
Do the addition problems and  fill up the number name of the answer
Apply addition of two-digit numbers in solving puzzles
Understand the addition problems from the clues given and solve them
Complete the activities in the given time
Do the activities independently
Express verbally and through actions, expressions, or gestures
Enjoy teamwork, appreciate others, and are willing to learn from others

Home Activity: Find the Difference

Assessment Worksheet: Find the total – Coming soon

Assessment Worksheet: Find the total (Enlarged) – Coming soon

Teacher Resource Document – Coming Soon

Source and Attribution of images:
All images used in the above Assets and Aids are originally created.
This digital material has been developed by the Sri Sathya Sai Vidya Vahini Inclusive Education Project, a unit of Sri Sathya Sai Central Trust, Prasanthi Nilayam, as a collaborative offering in the service of our nation.