Lesson Notes By Weeks and Term v4 - JHS 3

Lesson Video

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Performance objectives

• Define ratios and proportions.
• Understand the concept of enlargement.
• Solve problems involving enlargement using ratios.
• Apply this knowledge to real-life situations in Ghana.

Lesson summary

This lesson introduces the concept of enlargement, a fundamental idea in geometry and a practical tool in everyday life. Enlargement is a type of transformation that changes the size of an object while keeping its shape the same. We see it everywhere in Ghana: from the architect's plan for a new house in East Legon, to the zoom feature on our phones when looking at a picture from the Aboakyer festival, to a small Kente design sketch being woven into a large cloth. By understanding enlargement, we learn how to scale things up proportionally, a skill used in art, design, engineering, and even cooking.

Lesson notes

A. What is Enlargement?

Enlargement is a transformation that produces an image that is the same shape as the original object but a different size. Think of it as "zooming in". Object: This is the original, starting shape. Image: This is the new, enlarged shape after the transformation.

Key Properties of an Enlargement: The angles in the image are the same as the corresponding angles in the object. (The shape is not distorted). The lengths of the sides of the image are all multiplied by the same number. This number is called the scale factor. The object and its image are similar shapes. B. The Scale Factor (k)

The scale factor (often denoted by the letter 'k') is the ratio that tells us how much larger the image is compared to the object. For an enlargement, the scale factor is always greater than 1 (k > 1).