2TH §3.5 Mixed exercises

§ 3.5 Mixed exercises today!
First let's look back at a difficult exercise from
§ 3.4:   exercise 30, page 112.
Open your Textbook!
Open your Notebook, too.
MAKE 30a now!
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Slide 1: Slide
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This lesson contains 13 slides, with interactive quizzes and text slides.

time-iconLesson duration is: 50 min

Items in this lesson

§ 3.5 Mixed exercises today!
First let's look back at a difficult exercise from
§ 3.4:   exercise 30, page 112.
Open your Textbook!
Open your Notebook, too.
MAKE 30a now!

Slide 1 - Slide

timer
1:00

Slide 2 - Slide

Answer to 30a What is the factor to multiply the sides of PQRS by to get KLMN, is ..........
A
9
B
3
C
9
D
31

Slide 3 - Quiz

Do you remember from §3.4 ?
When discussing two SIMILAR figures, then
- the dimensions are multiplied by, say k
- the perimeter is also multiplied by k, however
- the AREA is multiplied by 
k2

Slide 4 - Slide

30a The solution:
1st: calculate the factor to get from area PQRS to area KLMN.
That is 144 : 16 = 9
2nd: Take the ROOT of 9, to get the SCALE FACTOR from PQRS to KLMN
So: Root 9 = 3 = Scale Factor!

Slide 5 - Slide



Now MAKE 30b in your Notebook!

timer
2:30

Slide 6 - Slide

30b The solution:
Let's keep it as simple as it can be.
(The Solutionsbook, normally very good, gives a pretty difficult solution...)
We make a table for the possibilities of the squares. 
We start with the area of 16 squared cm, because that has very few possibilities. Only 3, see next slide!

Slide 7 - Slide

All possibilities follow here:
                            PQRS:                        KLMN:
1st:              1 cm x 16 cm         3 cm x 48 cm
2nd:            2 cm x 8 cm          6 cm x 24 cm
3rd:             4 cm x 4 cm          12 cm x 12 cm                            

Slide 8 - Slide

Slide 9 - Slide

Now a few questions about § 3.5,
today's homework.

Slide 10 - Slide

Many exercises ask you to calculate the lengths of sides.
What is the best method for this?
A
Calculator
B
Make a ratio table
C
Hugging your neighbour
D
Comparing the angles

Slide 11 - Quiz

Now do § 3.5!
Exercises 33, 35 and 36 (page 114)
timer
15:00

Slide 12 - Slide

I want you to be COMPLETE in 33:

1. Calculate the unknown angles 
2. Draw the second picture in the same shape
3. Make a ratio table and fill in the matching lengths
4. Calculate the scale factor for the matching lengths
5. Conclusion: are the quadrilaterals similar or not?

Slide 13 - Slide