How to Find the Scale Factor of a Dilation?

Dilation is possible using the scale factor, which helps to increase or decrease the size of the object. A scale factor is a number by which the size of any shape or geometric figure can be changed relative to its original size.

Related Topics

• How to Graph Transformation on the Coordinate Plane: Dilation?

Step by step guide to finding the scale factor of a dilation

Dilation is the process of resizing or transforming an object. It is a transformation that makes the objects smaller or larger with the help of the given scale factor. The new figure that is obtained after dilation is called the image and the main image is called the pre-image. Dilation can be of two types:

• Expansion – When the size of an object is increased.
• Contraction – When the size of an object is decreased

Center of dilation

Dilation geometry has an important concept called the “center of expansion”. Dilation transforms the size of the figure which may increase or decrease. Resizing occurs from a point called the center of dilation. It is the center of dilation from which objects/shapes expand or contract.  In the figure shown below, the triangle is enlarged from the center of dilation which is marked as \(R\).

The scale factor

A scale factor is a number by which the size of any geometrical figure or shape can be changed relative to its original size. It is the ratio of the sizes of the original figure with the dilated figure.

The scale factor can be denoted by \(r\) or \(k\).

• The image is enlarged if the scale factor is more than \(1 (k > 1)\).
• The image is contracted if the scale factor is less than \(1 (0< k <1)\).
• The image remains the same if the scale factor is \(1 (k = 1)\).

Note: The magnitude of the scale factor is considered and the scale factor cannot be zero.

Scale factor formula

The scale factor can increase the size of an object or decrease the size of an object. The basic formula to find the scale factor of a dilated figure is:

\(\color{blue}{Scale\:factor\:=\:Dimension\:of\:the\:new\:shape\:\div \:Dimension\:of\:the\:original\:shape}\)

This formula can be written in another way that helps to find the dimensions of the new shape:

\(\color{blue}{Dimensions\:of\:the\:original\:shape\:×\:Scale\:factor\:=\:Dimension\:of\:the\:new\:shape}\)

Exercises for Finding the Scale Factor of a Dilation

• The length of each side of the square is \(6\) units. If the scale factor is \(3\), what will be the length of each side of the expanded square?

• Find the scale factor of the dilation.

1. \(\color{blue}{18}\)
2. \(\color{blue}{2}\)