1TH/Vwo §6.5 Comparing graphs - MORE

• Wiskunde
• Middelbare school
• havo, vwo
• Leerjaar 1

§7.5 Comparing graphs - MORE

This Lessonup 

is about the 2nd part of  §7.5 Comparing graphs.

First let's look at one exercise:

number 31, p.221 is the one!

Let's see if you remember how it was!

Task 1:

Give your answer to 33a in the next slide.

Task 1: Jean's better off ...

1. with Vital
2. it depends
3. with Hydro
4. this is not clear

Solution Task 1: (33a)

Task 2:

Give your answer to 33b in the next slide.

Watch the vital word: 'INCREASE'!

Task 2: (33b) answer:

1. more than 225
2. more than 200
3. more than 35
4. more than 165

 Solution Task 2: (33b)

What is the number 200 doing in the calculation?

For more than 200 cubed metres Vital is cheaper. 

So, to explain it a little differently: for more than 165 + 35 = 200 cubed metres

Vital is cheaper, so the answer is:  a 35 cubed metres INCREASE!

We go on with 2 graphs in one coordinate system.

In PART ONE the emphasis (=nadruk) was on comparing them.

Now we concentrate on the POINT OF INTERSECTION (p.o.i.) of both graphs! 

Task 3:

Read off the p.o.i. of both 

graphs.

Key in in next slide.

task 3: The p.o.i. is .......

1. (5, 4)
2. (3 1/2, 5)
3. (5, 3.5)
4. (5, 3 1/2)

Explanation Task 3:

Read off the p.o.i. of both 

graphs.

Key in in next slide.

Explanation: 

First we write down the HORIZONTAL

coordinate; only then the VERTICAL one.

So we get:  (5, 3  1/2)   or   (5, 3.5)   Don't forget the brackets!

There are 2 ways to get to know the points of intersection:

Reading off  p.o.i.      or         Calculating p.o.i.

But ...... when to do what?!

Why calculating, if you can read off ??!

Read below, why.

Many times the p.oi. from 2 graphs is hard to read off.

For instance:

you read off (3, 7) but in fact the p.o.i. turns out to be

(3.1 , 6,9) !

In fact CALCULATING is more exact -better- than reading off.

From READING OFF we now move to CALCULATING the p.o.i.!

That is what you are going to do on p.222.

Task 4:  Fill in number = 5 in the green formula.

The green graph has this formula:

6 - number x 0.5 = length

What is the length when 

you fill in  number = 5 ?

Fill in in next slide!

1. 1.5
2. 3.5
3. 2.5
4. 5

Solution Task 4:  Fill in number = 5 in the green formula.

Task 5:  Fill in number = 5 in the red formula.

From the graph you can read off the red formula too:

number x 0.5 + 1 = length

Fill in number = 5 in this formula.

What does the length become?

(Fill in in next slide!)

1. 2.5
2. 1.5
3. 3.5
4. 3

Explanation Task 5:  Fill in number = 5 in the red formula.

 The green formula :

number x 0.5 + 1 = length

Summarising (1)  what we just did:

Summarising (2).

It is about the difference between 

a. reading off  and. b. calculating:

Task 6: In order to do 33a and 34, what should you do first? Answer in next slide.

What to do first?

Solution Task 6:

Make a TABLE!

For 36a even make a DOUBLE TABLE,

 as there are 2 graphs!

Homework time

Make:  32,  33,  34 and 35 now.

Take a few pictures and send them in in GC.