### Home > CC3 > Chapter 8 > Lesson 8.3.1 > Problem 8-128

The two triangles at right are similar shapes. Homework Help ✎ What is the scale factor between shape A and shape B?

Find the missing sides.

If you wanted to make shape A smaller instead of bigger, what is a scale factor you could use?

Which corresponding sides in A and in B are both known?

What do you need to multiply 8 by to get 20?

Identify which sides in A correspond to which sides in B.

Since 16 corresponds to *t* and *s* corresponds to 35, multiply 16 by the scale factor to find *t*, and divide 35 by the scale factor to find *s*.

The scale factor is what you multiply by to increase or decrease the size of a shape.

If a scale factor greater than one created a larger triangle, then a scale factor less than one must create a smaller triangle.

Note that a scale factor cannot be negative because a negative side length is nonexistent.