Geometry - Similar Triangles & Scale Factors

Maths - Year 9 Australia

Similar Triangles

In similar figures: All pairs of corresponding sides are in the same ratio. All pairs of corresponding angles are equal.

Scale Factor

The ratio of distances between the larger and smaller figures.

Scale Factor on a Cartesian Plane

1. Choose 2 Corresponding sides

2. Measure them Horizontally

3. Apply in Scale Factor Formula

Finding Unknown

1. Determine corresponding sides

2. Find the scale factor with known sides

3. Multiply leftover side by scale factor

4. Answer = Unknown

Scale and Area (Finding Area)

1. Find the scale factor

2. Multiply the area by the scale factor SQUARED

Scale and Volume (Finding Area)

1. Find the scale factor

2. Multiply the area by the scale factor CUBED

Scale and Area (Finding Side - Hard One)

1. Unknown side squared over known side = Area for shape w unknown side over other one

2. Simplify by dividing 2nd fraction

3. Divide both sides by bottom no of fraction

4. Remove square from unknown side and square root the number

5. That is answer

Scale and Volume (Finding Side - Hard One)

1. Unknown side cubed over known side = Area for shape w unknown side over other one

2. Simplify by dividing 2nd fraction

3. Divide both sides by bottom no of fraction

4. Remove square from unknown side and cube root the number

5. That is answer