### Lesson Plan: Enlargement and Reduction of Plain Figures
**Grade:** Senior Secondary 1
**Subject:** Technical Drawing
**Duration:** 60 minutes
**Topic:** Enlargement and Reduction of Plain Figures
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#### **Objectives:**
By the end of this lesson, students will be able to:
1. Understand the concepts of enlargement and reduction.
2. Apply scale factors to modify the size of plain figures.
3. Use technical drawing tools to create accurate enlarged and reduced figures.
4. Calculate new dimensions of figures after enlargement or reduction.
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#### **Materials Needed:**
- Graph paper
- Rulers
- Compasses
- Protractors
- Pencils
- Erasers
- Calculators
- Whiteboard and markers
- Enlarged and reduced figure examples (printouts or in the textbook)
- Projection screen or drawing board
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#### **Introduction (10 minutes):**
1. **Greeting and roll call.**
2. **Recap of Previous Lesson:** Briefly review the last topic covered to make a connection.
3. **Introduction to Topic:**
- Define `Enlargement` and `Reduction`.
- Explain where and why these concepts are used in technical drawing (e.g., architecture, engineering).
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#### **Instruction (20 minutes):**
1. **Explanation of Concepts:**
- Define `Scale Factor` and how it affects the size of a figure.
- Differentiate between enlargement (scale factor > 1) and reduction (scale factor < 1).
2. **Illustration with Examples:**
- Draw a simple geometric shape (e.g., rectangle) on the whiteboard.
- Show how to apply different scale factors to enlarge and reduce this rectangle.
- Discuss how each dimension is altered proportionally by the scale factor.
3. **Calculation Practice:**
- Provide a sample geometric figure with dimensions.
- Demonstrate step-by-step calculations to determine the new dimensions after applying a scale factor for both enlargement and reduction.
- Emphasize maintaining the aspect ratio.
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#### **Guided Practice (15 minutes):**
1. **Class Activity:**
- Hand out graph paper and technical drawing tools.
- Assign a simple figure (e.g., a triangle) with given dimensions.
- Instruct students to choose a scale factor (e.g., 2 for enlargement, 0.5 for reduction) and calculate the new dimensions.
- Students should then draw both the original and the modified figures on graph paper.
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#### **Independent Practice (10 minutes):**
1. **Worksheet:**
- Provide a worksheet with various plain figures and designated scale factors.
- Require students to calculate new dimensions and draw both the original and modified figures.
- Encourage the meticulous use of technical drawing tools for accuracy.
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#### **Assessment and Evaluation (5 minutes):**
1. **Review of Student Work:**
- Collect worksheets and check for accuracy in calculations and drawings.
- Provide immediate feedback to students to address any misunderstandings.
2. **Quick Quiz:**
- Give a short quiz with problems on enlargement and reduction, which students complete individually.
- Possible problems: calculating dimensions for given scale factors, identifying correct scale factors, etc.
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#### **Closure (5 minutes):**
1. **Summary:**
- Recap the key points of the lesson: definitions, scale factors, application in drawing.
- Highlight the importance of precision in technical drawing.
2. **Homework Assignment:**
- Assign a few figures to be enlarged and reduced, to reinforce learning.
- Encourage students to bring any questions to the next class.
3. **Next Lesson Preview:**
- Give a brief overview of the next topic to generate interest.
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#### **Extension for Advanced Students:**
- Challenge advanced students to apply enlargement and reduction concepts to more complex figures (e.g., composite shapes), or to solve real-world problems (e.g., scaling a floor plan).
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By following this lesson plan, students will gain a foundational understanding of how to manipulate the size of plain figures, a crucial skill in technical drawing.