# Definition of scale factor

A scale factor is the ratio of sizes of two similar figures. For example, the scale factor is 2 for the following two similar figures.

The scale factor is 2 because the triangle on the right is two times bigger than the triangle on the left.

How to find the scale factor

- Decide which figure is the original figure.

- Make a ratio of corresponding sides. Scale factor is equal
**new figure** divided by **original figure**.

3.Simplify, if possible.

For the two similar figures above, the original figure is the triangle on the left.

A ratio of corresponding sides is equal to 16/8 or 2.

If on the other hand, we make the triangle on the right our original figure, the scale factor is 8/16 or 1/2.

If the triangles are not similar, then you cannot find the scale factor

When two figures are identical in size, the scale factor is equal to 1.

When a figure is shrunk, the scale factor is less than 1.

When a figure is enlarged, the scale factor is bigger than 1.

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