Enlargement
(KS3, Year 7)

The Lesson

An enlargement resizes a shape. An enlargement makes a shape larger or smaller. An enlargement is a type of transformation.

A Real Example of an Enlargement

It is easier to understand enlargement with an example. The diagram below shows an enlargement of a shape. The shape before the enlargement (called the object) is in light blue. The shape after the enlargement (called the image) is in dark blue:

In this example, the shape has been enlarged with a center of enlargement (shown as a red cross) at the origin.

Properties of Enlargement

  • Each side of the object is scaled by a scale factor. If an enlargement has a scale factor of 2, each side of the image is 2 times larger than the sides of the object.
  • The length of sides remain in the same proportion to each other.
  • Each line in the image is parallel to the corresponding line in the object.
  • All angles remain the same in the object and the image.

Enlarged Shapes Are Similar Shapes...

If a shape is enlarged, the shapes are similar. Similar shapes are the same shape but not the same size.

...But Not Congruent Shapes

Congruent shapes are the same shape and the same size.

If a shape has only been translated, reflected or rotated (or some combination of all three) then the shape is congruent.
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See Also

What is geometry? What are transformations?