# 1TH/vwo §7.1 From description to formula

What is due, this lesson?
+ Ch 7 is on the menu the coming lessons.

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Slide 1: Tekstslide
WiskundeMiddelbare schoolhavo, vwoLeerjaar 1

In deze les zitten 24 slides, met interactieve quizzen en tekstslides. Lesduur is: 50 min

## Onderdelen in deze les

What is due, this lesson?
+ Ch 7 is on the menu the coming lessons.

#### Slide 1 -Tekstslide

First....
an amazing nature event !

#### Slide 4 -Tekstslide

a. We read this text together.
b. Answer the question below in the next slide.

#### Slide 5 -Tekstslide

Roughly how far away is the thunderstorm?
A
2 km
B
2 + 2/3 km
C
2.5 km
D
3 km

#### Slide 6 -Quizvraag

Solution:
It takes the thunder 3 seconds to travel 1 km.
So if you hear the thunder after 8 seconds, then it is
8 : 3 = 2  2/3 km away. Or 2.7 km, rounded off.
However, because the question said 'roughly' (ongeveer) also
2.5 km is a good answer.

#### Slide 8 -Tekstslide

A rule in words about thunder and lightning is:
If you divide the time in seconds the thunder takes to reach you by 3, you get the distance in km.

#### Slide 9 -Tekstslide

This Rule in Words is changed into a Formula now:
We alredy have a RULE IN WORDS:
If you divide the time in seconds the thunder takes to reach you by 3, you get the distance in km.
Now we make a FORMULA:
time in seconds : 3 = distance in km

#### Slide 10 -Tekstslide

What does a Formula have, but a Rule in Words does not?

#### Slide 11 -Woordweb

Solution:
A Formula has arithmetic symbols like:
+           -              x      :      and      =
What is described (=beschreven)  in a Rule in Words, is made into a Calculation in a Formula.

#### Slide 14 -Tekstslide

Let's make a Formula now!
In the next exercise you get some information.
A) to make a Formula and then
B) to make a Calculation with it.
By the way: a Formula should be applicable (toepasbaar) for any number that you like to fill in.
For every number another outcome will follow.
A Formula does not have one fixed outcome!

#### Slide 15 -Tekstslide

START your Formula with:
Weight of a box =  .............................
Note: You can also END your Formula by it, so like this:
..................................... =  Weight of a box.

Formula .... ?

#### Slide 17 -Woordweb

The correct Formula is:

number of balls x 60 + 250 = weight,  or
250 + number of balls x 60 = weight,  or
weight = number of balls x 60 + 250
So you see that there are more ways to write it down!

#### Slide 19 -Tekstslide

Now answer this one, using the Formula you just made!

#### Slide 20 -Tekstslide

Calculate the weight of a box containing 6 balls.
The Formula is:
number of balls x 60 + 250 = weight
A
600
B
590
C
580
D
610

Solution:

#### Slide 22 -Tekstslide

Summarising:
Sometimes you have a Description or a Formula in Words (that's the same).
You can change this into a Formula.
In a Formula you can fill in a given number, to get an outcome.
Like we just did.

#### Slide 23 -Tekstslide

Homework time
Time to do §7.1 now.
You may skip 6, as we just did this one.
Don't forget to
+ check with the Solutionsbook    +    take pics and
+ send it in in GC.