1. February 1, Math 201
OBJECTIVE: Students will be able to calculate the length of corresponding sides of similar triangles, using proportional reasoning
AIM: How do we write a proportion from corresponding sides of similar triangles?
STANDARDS: 6.G.1
PRIOR KNOWLEDGE: Jason and Richie ran at the same rate. If Jason covered 5 miles in one hour, how many miles did Richie cover after running for 3 hours?

2. Similar triangles have the same shape, but they don’t have to have the same size. Angle measures are equal and corresponding sides are proportional.
In the figures above, the triangles are similar, so the corresponding sides are proportional. We write

3. Review question: If some length is “proportional” to some other length, what does that mean? What is the relationship between the two lengths?
You can find an unknown side length of a triangle by setting up and solving proportions resulting from similar triangles.

4. Example 1
Set up a proportion for the sides of these similar triangles so that you can solve for the length of the missing side JK
Strategy: Write a proportion from the corresponding sides.
Which sides are corresponding sides?

5. Write the proportion between the corresponding sides we are talking about.
Substitute the known lengths to write the proportion to find the length of side JK
Example 2 Solve the proportion in example1
Cross-multiply to solve the proportion. What number times
= 48?
Solution: The length of JK is

6. Group work with a partner: Handout
Review handout problem
Homework: