Unit D: Two-Dimensional Shapes

Topic 9: Congruence

9-1: Translations

Key Concept

A transformation is a change in the position, shape, or size of a figure. The blue triangle is larger and is in a different position than the black triangle.

A rigid motion is a transformation that changes only the position of the figure. The blue triangle has the same shape and size as the black triangle, but a different position.

An image is the result of a transformation of a figure. To identify the image of a point, use prime notation. The image of point A is A′] (read “A prime”).

A small black triangle to the left of a larger blue triangle.

A black triangle to the left of a blue triangle of the same size.

A black triangle with vertices A, B, C to the left of a blue triangle of the same size with corresponding vertices A´, B´, C´.

Part 1


A translation, or slide, is a rigid motion that moves every point of a figure the same distance and in the same direction.

Every point of the black triangle moves 5 units to the right and 5 units down.

A graph of a translation.

Example Recognizing and Describing Translations

Find the transformation that is a translation. Describe in words the translation that maps ΔABC to its image ΔABC′.

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Table of Contents

Digits, Grade 8, Volume 2, Homework Helper Unit D: Two-Dimensional Shapes Unit E: Measurement and Data Unit F: Personal Financial Literacy Unit G: Step-Up Lessons English/Spanish Glossary Formulas Math Symbols Formulas Measures Properties