Unit 1 - Day 5:

Day 5:

Daily Objective: Students know similar figures and find missing lengths from them. 

Similar figures: Similar figures are two figures that have the same shape but can be a different size. When two figures are similar, the ratios of their lengths corresponding sides are equal.

In order to find the missing sides you need to set it up in a proportion, by using the X method. So this example the problem would look like this:

    6  =  X 

   10    5

Once you have this equation down you need to cross multiply the numbers so the equation would be 6x5 = 10x so 10x = 30. 30 divided by 10 is 3. Therefor x = 3. So the length of that side of the trangle is 3.

In these similar figures answer these questions:

Does AB = DE? 

Does AC = DF? 

How do you set the equation up?

Yes AB = DA , Yes AC = DF 

The equation is AB over AC and DA over DF. 

Quiz :

Quiz : Answers :

Question 1 : Find the length of x. 

       1.) Set the equation up ; 50 = 7

                                              x      7

       2.) Now you need to cross multiply 7x = 50 x 7

       3.) 50 x 7 = 350 and now you need x alone so 350 divided by 7 = 50

       4.) So the length of x is 50

Answer: 50 units

Question 2 : The two rectangles are similar. The ratio of their areas is 9:16 find the missing side. 

       1.) Set the equation up :  9   =  20 

                                             16        x

       2.) Now cross multiply : 9x = 20 x 16.

       3.) 20 x 16 = 320 

       4.) 320 / 9 = 35.5, so X = 35.5

       5.) So X is 35.5 , the missing length is 35.5 

Answer: 35.5 units

Question 3 : Find the area of the trapezoid.
       1.) Use the formula B1 + B2 x H
                                            2
       2.) Plug in the numbers to the formula : 10 + 20 x 5
                                                                           2
       3.) 10 + 20 = 30 /2 = 15
       4.) 15 x 5 = 60.
       5.) The area will be 60 units

Answer: 60 units