Scale Drawings Area & Perimeter

The area of a polygon measures the amount of space it covers.

The perimeter of a polygon measures the outer band of the polygon.

Scale factor is the ratio by which a polygon changes size.

Scale factor is used as a constant of proportionality after converting it to a unit rate, so we can use the equation, y = kx.

We modify this as actual, a, equals k, scale factor, times the drawing, d or a = kd.

If a drawing has a scale of 3 cm to 9 feet, what is the scale factor (from drawing to actual)?

In this question, the parenthesis are important. Scale factor changes depending on the direction. When going from a drawing to an actual, scale factor should be > 1. When going from an actual to a drawing, scale factor should be < 1.

When finding area or perimeter of a shape AND you have a scale factor, do the following:

1. Determine scale factor, if not explicit
2. Scale all dimensions of the shape
3. Solve for area/perimeter.