Finding the scale factor
Proportions can be used to compare lengths of different sized shapes. To work out how much bigger a shape is compared to a smaller one, divide the bigger length by the corresponding smaller length. This will give you the scale factor of enlargement.
Example
A rectangle has been enlarged. Find the scale factor of enlargement.
To find the scale factor of enlargement, divide one of the larger lengths by the corresponding smaller one.
\(5 \div 2 = 2.5\)
The bigger rectangle is larger than the smaller one by a scale factor of 2.5.