2Tvwo § 4.5 Mixed exercises

§ 4.5 Mixed exercises   today!
First let's look back at a difficult exercises from
§ 4.4:   exercise 30, page 140.
Open your Textbook!
Open your Notebook, too.
MAKE 30a now!
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Slide 1: Slide
WiskundeMiddelbare schoolvwoLeerjaar 2

This lesson contains 16 slides, with interactive quizzes and text slides.

time-iconLesson duration is: 50 min

Items in this lesson

§ 4.5 Mixed exercises   today!
First let's look back at a difficult exercises from
§ 4.4:   exercise 30, page 140.
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
root 9
B
3
C
9
D
1/3

Slide 3 - Quiz

Do you remember from §4.4 ?
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

30 a The solution:
1st we calculate the factor by which to multiply area PQRS by to get area KLMN.
That is 144 : 16 = 9
2nd We know that we have to 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!
Remember that is was a Homework task for today!
timer
2:30

Slide 6 - Slide

30b The solution:
Let's keep it as simple as 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 § 4.5,
today's homework.

Slide 10 - Slide

Question about 31, page 142:
What Method is needed here?
A
Finding all squares from numbers 1 to 9.
B
Checking angles and sides too.
C
Checking if the angles are equal.
D
Checking the sides.

Slide 11 - Quiz

I want you to be COMPLETE in 31a:

1. calculate the unknown angles 
2. make pairs of equal angles
3. make a ratio table for finding a ratio table (if there is one!)
4. conclusion: are the quadrilaterals similar or not?

Slide 12 - Slide

Read 32a carefully.
NOTE: we start from the real Dutch parts and
end at the models in Madurodam.
What is the best answer to it?
A
1/25
B
0.04
C
25
D
1:25

Slide 13 - Quiz

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 14 - Quiz

Mistake in 36!
Correct the following mistake, but only with a PENCIL!!
'In rectangle ABCD, triangle ABD is an enlargement of triangle ADE.'
In this sentence, the triangles should be exchanged.
Change this in a neat way, only with a pencil.

Slide 15 - Slide

Now do § 4.5!
timer
15:00

Slide 16 - Slide