Scale and Scale Factor

Front

What is a scale factor?

Back

A scale factor is a number that describes how much a figure is enlarged or reduced in size. It is the ratio of the dimensions of the model to the dimensions of the actual object.

Front

How do you calculate the scale factor?

Back

To calculate the scale factor, divide the size of the model by the size of the actual object. For example, if a model is 2 inches tall and the actual object is 4 feet tall, the scale factor is 2 inches / 48 inches = 1:24.

Front

If a doghouse is 3 feet tall and a model is 0.5 inches tall, what is the scale factor?

Back

1:72

Front

If a tree house is 10 feet tall and a model is 6 inches tall, what is the scale factor?

Back

1:20

Front

If George Washington's face is 60 feet tall and a model is 60 inches tall, what is the scale factor?

Back

1:12

Front

True or False: All triangles are similar.

Back

False

Front

What does it mean for triangles to be similar?

Back

Triangles are similar if they have the same shape but not necessarily the same size. This means their corresponding angles are equal and their sides are in proportion.

Front

If triangle ABC is similar to triangle EFG and angle A measures 25 degrees, what can you say about angle E?

Back

Angle E also measures 25 degrees because corresponding angles in similar triangles are equal.

Front

If angle A is 25 degrees and angle F is 100 degrees in similar triangles, what is the measure of angle C?

Back

55 degrees.

Front

What is the relationship between scale factor and area?

Back

The area of similar figures is proportional to the square of the scale factor. If the scale factor is k, then the ratio of the areas is k^2.