Use the enlargement transformation to explain similarity and develop the conditions for triangles to be similar (ACMMG220)

LO: To use the enlargement transformation to explain the conditions of triangles to be similar.


  • That enlargement is the increase in size of an object.

  • Triangles are a 3-sided and 3-angled shape.


  • That the enlargement transformation keeps certain aspects of the shapes the same but also changes some other aspects.


  • I can use the enlargement transformation to explain the conditions of triangles.

Enlargement Transformation

An enlargement is a transformation which changes the size of an object without changing its shape.

In Geometry, two shapes are considered to be similar when the only difference is size (and possibly the need to move, turn or flip one around).

Everyday uses of enlargement include zooming into a picture, using Google Maps. The original object does not change it’s size or shape, just our version of the object changes.

Similar objects can be larger or smaller in size. It doesn’t always have to be larger!

These butterflies demonstrate enlargement.

These triangles also demonstrate enlargement.

The objects in the same colour are similar figures.

Teaching Activities


Enlargement Videos

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