Unit 1 - Day 7:

Day 7:

Daily Objective: Students will know what similar triangles are.

Triangles are similar if they have the same shape but are different sizes.

In order to be able to find the area or one side of the trianlge you need to have a similar triangle to compare it to and use its ratio.

video: http://www.youtube.com/watch?v=gQoNjgayoLI

In order to find x you need to use the similar triangles and put them into a ratio/ use cross multiplication. The equation would be set up like this ..  9  =  X 

                                                                                                        4      2 

So 4x = 9x2 which is 18. 18/4 = 4.5 the ratio is 1:2

Quiz :

Quiz : Answers:

Question 1: These figures are similar. The area of triangle ABC is 850 square ft. Find the area of triangle DEF.

       1.) Set up the equation :    30   =   40  

                                              850        X

       2.) Cross multiply these numbers. 

       3.) New equation : 30x = 830 x 40 which is 34000

       4.) 34000 / 30 = 1133.33 

Answer : 1133.33 ft squared

Question 2: Find the area of the small figure given. The area of the large is 72 square inches. The triangle are similar.

       1.) Set up the equation :  6  =  12 

                                             X     72      

       2.) Cross multiply these numbers.

       3.) New equation : 12x = 72 x 6 which is 432

       4.) 436/12 = 36

Answer : 36 in. squared

Question 3: Find the value of X if the triangles are similar

       1.) Set up the equation :  6  =  4 

                                            12     x

       2.) Cross multiply these numbers.

       3.) New equation : 6x = 12 x 4 which is 48

       4.) 48 / 6 = 8 .

Answer: 8 un. squared