Similar Figures and Scale Factors

Front

What is a scale factor?

Back

A scale factor is a number that scales, or multiplies, some quantity. In geometry, it is the ratio of the lengths of two corresponding sides of similar figures.

Front

If the scale factor is greater than one, what happens to the new figure?

Back

The new figure will be an enlargement.

Front

If the scale factor is less than one, what happens to the new figure?

Back

The new figure will be a reduction.

Front

What does it mean for two figures to be similar?

Back

Two figures are similar if they have the same shape but not necessarily the same size, and their corresponding angles are equal.

Front

Are all angles in similar figures congruent?

Back

True, all corresponding angles in similar figures are congruent.

Front

What is the relationship between the sides of similar figures?

Back

The ratios of the lengths of corresponding sides of similar figures are equal.

Front

If a triangle has sides of lengths 3, 4, and 5, what are the sides of a similar triangle with a scale factor of 2?

Back

The sides of the similar triangle will be 6, 8, and 10.

Front

How do you find the missing side of similar figures?

Back

Use the proportion of the corresponding sides to set up a ratio and solve for the missing side.

Front

If one side of a triangle is 9 cm and the corresponding side of a similar triangle is 3 cm, what is the scale factor?

Back

The scale factor is 1/3.

Front

What is the formula to calculate the area of similar figures?

Back

The area of similar figures is proportional to the square of the scale factor.