This activity allows students to reason about ratio tables, which helps their understanding of what a ratio describes in a context and what quantities in equivalent ratios have in common.

In this TI-Nspire™ lesson, students learn that ratios are connected to geometry in multiple ways. When one figure is an enlarged or reduced copy of another by some scale factor, the ratios of corresponding lengths between the figures are proportional in accordance with that scale factor. The internal ratio of two sides in one figure is equivalent to the ratio of the corresponding two sides in the second figure. To find unknown lengths from known lengths, students can set up proportions in tables or equations.

Prior to working on this lesson, students should understand:

• understand how to find the perimeter and area of a rectangle;
• be able to write equations to describe proportional relationships.

This is Lesson 15 out of 15 in the Building Concepts in Mathematics: Ratios and Proportional Relationships Series.