Unit 1: Day 5

Day 5: What are Similar Figures and finding different lengths

A lot of today will mimic the lesson from day 2 with dilations and similar figures

Similar figures help us find the size of a bigger or smaller shape if we have at least 2 dimensions. 

The dimensions you use to prove the figures are similar can be any of the following 

• 2 side lengths
• Area and a side length
• 2 angles (in polygons besides squares/ rectangles)
• An angle and the area
• Any other 2 measurments

From there you set up a fraction: x = x

                                                 y    y

and cross- multiply to find the unknown variable or find if 2 shapes are the same. 

Once you find this, you can use the math to find other unprovided measurments.

For example, if the half- circles are similar, you could then use that information to find the area and perimeter of the triangle.

Quiz Time!

 1. Find the height of the tree.

2.Are these triangles similar?

3. What is the length of x?

Key:

1. 15 ft tall ( put the two fractions equal to each other and solve by cross multiplication) 

2. Yes, the ratio is 1:2 

3. 12 cm (use the cross multiplication method)