# Session 22: Decimal- addition & subtraction

<div align="left" dir="ltr" id="bkmrk-session-title-decima"><table style="width: 116.785714%;"><tbody><tr><td class="align-center" style="width: 32.79769%;">**Session Title**

</td><td class="align-center" style="width: 67.3215%;">**Decimal- addition &amp; subtraction**

</td></tr><tr><td style="width: 32.79769%;">Objective

</td><td style="width: 67.3215%;">1. Students will be able to:
2. Align and compute decimal numbers in addition and subtraction.
3. Apply these operations in real-world contexts.

</td></tr><tr><td style="width: 32.79769%;">Topics

</td><td style="width: 67.3215%;">1. Place value of decimal numbers
2. Decimal addition
3. Decimal subtraction
4. Aligning decimals in operations

</td></tr><tr><td style="width: 32.79769%;">Materials required

</td><td style="width: 67.3215%;">1. Whiteboard and markers
2. Decimal place value chart
3. Printed worksheets
4. Flashcards for puzzle match activity

</td></tr><tr><td style="width: 32.79769%;">Methodology

</td><td style="width: 67.3215%;">Guided practice with real-life problem solving

</td></tr><tr><td style="width: 32.79769%;">Session Duration

</td><td style="width: 67.3215%;">90 minutes

</td></tr></tbody></table>

</div>### Introduction Activity (30 minutes):

**Decimal Price Tag Game(15 minutes)**

Purpose: Activate prior knowledge and build context.

**Setup:**

Bring 5–6 small classroom items (e.g., pencil, eraser, notebook).

Label each with a price tag (e.g., $0.75, $1.20, $2.50, etc.).

**Instructions:**

1. Give each student or group a “shopping budget” (e.g., $5.00).
2. Ask them to “buy” 2–3 items and calculate the total cost and change from $5.00.
3. Discuss answers and write sample calculations on the board.

Transition:

"To shop smart, you need to be able to add and subtract decimal prices correctly. Today, we’ll learn how to do that like pros!”

**2. Concept Teaching (15 minutes)**

**A. Place Value Review:**

- Draw a place value chart on the board (Ones, Tenths, Hundredths, Thousandths).
- Ask students to place digits in the correct columns for 3.75, 0.08, etc.

**B. Key Concept:**

- Always line up decimal points when adding/subtracting.
- Add placeholders (zeros) if needed for consistency.

**Demonstration:**

 4.2   
\+ 1.35  
\------  
 5.55

Explain the importance of matching decimal places.

Repeat with subtraction:

 5.00  
\- 2.45  
\------  
 2.55

### Main Activity (40 minutes): 

**(20 minutes)**

**Addition**

- 1.3.25 + 4.75 - Answer: 8.00
- 5.6 + 2.85 - Answer: 8.45
- 7.4 + 3.19 - Answer: 10.59
- 0.78 + 6.22 - Answer: 7.00
- 9.03 + 1.97 - Answer: 11.00

**Subtraction**

- 6.75 – 3.25 - Answer: 3.50
- 9.8 – 4.56 - Answer: 5.24
- 7.6 – 2.39 - Answer: 5.21
- 8.25 – 5.18 - Answer: 3.07
- 10.4 – 6.73 - Answer: 3.67

**Word problems (20 minutes)**

<span style="color: rgb(224, 62, 45);">**Addition** </span>

**1. Shopping Problem** Emily bought a book for $12.75 and a pencil case for $3.50. How much did she spend in total?  
Answer: 12.75 + 3.50 = 16.25

**2. Distance Travelled** Sarah walked 3.6 miles to the park and then 2.8 miles to her friend's house. How many miles did Sarah walk in total?  
Answer: 3.6 + 2.8 = 6.4 miles

**3. Total Time Spent** John worked for 4.5 hours on Monday and 6.25 hours on Tuesday. How many hours did he work in total?  
Answer: 4.5 + 6.25 = 10.75 hours

<span style="color: rgb(224, 62, 45);">**Subtraction** </span>

**1. Money Spent** Mary had ₹20. She bought a book for ₹7.50. How much money does she have left?  
Answer: 20.00 – 7.50 = 12.50

**2. Time Left** The movie started at 7:00 PM and ended at 9:15 PM. How long was the movie?  
Answer: 9.15 – 7.00 = 2.15 hours (or 2 hours and 9 minutes)

**3. Distance Remaining** Kevin ran 5.3 miles in the morning and 2.8 miles in the afternoon. How many miles does he have left to run if his goal is 10 miles?Answer: 10.00 – (5.3 + 2.8) = 2.9 miles left

### Review Questions (10 minutes):

1. Why is it important to align decimal points before adding or subtracting decimal numbers?
2. How does place value help you when working with decimal numbers in addition and subtraction?

### Follow up tasks (10 minutes):

**Class Work**

**Problems (cut out the following into individual cards):**

- 3.25 + 1.75
- 6.4 – 2.15
- 5.85 + 4.15
- 9.1 – 3.6
- 7.35 + 2.65

**Answers (cut and mix these up too)**:

- 5.00
- 4.25
- 6.15
- 9.00
- 7.7

**Instructions:**

- Mix all problem and answer cards.
- Each team must match the correct answer to each problem.
- First team to complete the correct matches wins!

### Expected Learning Outcome: 

**Knowledge Building:**

By the end of the lesson, students will be able to:

- Add and subtract decimal numbers accurately.
- Align decimals correctly.
- Solve real-life word problems involving decimals

**Skills Building:**

- Problem-solving and self-checking