1TH/vwo §6.1 From description to formula

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

Today we do:

What is the learning goal today?

First....

an amazing nature event !

a. We read this text together.

b. Answer the question below in the next slide.

This is not an easy question.

So: concentrate! In the next slide

you may answer the

question.

Roughly how far away is the thunderstorm?

1. 2 km
2. 2 + 2/3 km
3. 2.5 km
4. 3 km

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 =                 km away. Or 2.7 km, rounded off.

However, because the question said 'roughly' (ongeveer) also

2.5 km is a good answer.

2+​3​​2​​

Question:

In which LINE a MISTAKE is made in this text? 

Key in the number of the line in the next slide!

TIP: it's not about words;

they are all correct. It's about

meaning of events.

The mistake is in the ..... line.

1. 1st
2. 3rd
3. 5th
4. 7th

The MISTAKE is:

At first they say that the lightning

comes first and the thunder follows.

However in the 3rd line it's 

the other way round:

The thunder is followed by the 

lightning!? Funny.

In the 13th edition of the book this mistake is corrected,

as you can see below:

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.

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 

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

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.

Let's make a Formula now!

In the next exercise you get some information.

You are asked 

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!

Examples of formulas:

-     salary in euros = hours x  15 euros  + 15

-     length of a tree in cm = years x 10 cm 

START your Formula with:

Weight of a box =  .............................     (the NUMBER OF BALLS plays a part here!)

  

Formula .... ?

Some correct Formulas are:

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!

The MAKING of a Formula ...

is more difficult than making CALCULATIONS with that

Formula. 

You will notice this in the next slides.     

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

In the next slide, the Formula is repeated.

ANS 

Calculate the weight of a box containing 6 balls.
The Formula is:
number of balls x 60 + 250 = weight

1. 600
2. 590
3. 580
4. 610

Solution:

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.

Homework time

Time to do §6.1 now.

You may skip exercises 1 and 2, as you already did a lot.

Don't forget to 

+ check with the Solutionsbook