1Tvwo Ch 9 §9-4 The calculator

• Wiskunde
• Middelbare school
• vwo
• Leerjaar 1

What is the main purpose of using the CALCULATOR ?

Task 1:
John orders Chips and Cola for himself and 6 friends.
Prices: Chips € 2 and Cola € 1.65
How to calculate the total cost?

1. cost = 2 + 1.65 x 7
2. (2 + 1.65) x 7 = cost
3. 7 x (2 +1.65) = cost
4. cost = (7 + 1.65) x 2

Explanation Task 1:

Both prices, 2 € and 1.65 €, have to be multiplied by 7, because all the 7 boys get Cola and Chips.

This is done by putting brackets over 2 + 1.65

Task 2:
Calculate, using your calculator:
a. 13.5 + 9.2 x 8.3 =

1. 89.68
2. 89.86
3. 98.86
4. 98.68

Task 3:
Calculate, using your calculator.
6.1 x (3.7 - 5.4) =

1. 13.07
2. 10,37
3. -10.37
4. -13.07

Task 4:
6.5 x 8.2 + 4.8 : 8 =

1. 35,9
2. 95.3
3. 39,5
4. 53.9

Comment on Task 2, 3 and 4

Calculating these exercises asks precision from you.

Not forgetting anything, for example brackets!

The funny thing is, you do not have to really understand anything about 'order of operations' for this task.

Your sillicone friend, the calculator, takes good care of that!

Task 5:
Write as decimal numbers, using your calculator.
Round to 3 decimal numbers.

​42​​28​​

1. 0.667
2. 0,667
3. 0.666
4. 0,666

Explanation task 5:

 To write          as a decimal number, rounding to 3 decimal numbers,

you  can do:    

 - key in:  '28 : 42 =' , followed by rounding,        

or: use the 'a  b/c' button, left column, 3rd from above:

     - key in:  '28  a  b/c  42 ='. Now you get your answer as a fraction!

To change this into a decimal number, key in:  a  b/c.

Finally round again.

​42​​28​​

Task 6:
Do the same with:
6

​9​​7​​

1. 7.668
2. 6.887
3. 6.778
4. 8.667

Explanation Task 6:
How to key in:    6       ?

Two ways:

               -        6 + 7 : 9 =        , or:

               -         6  a b/c   7  a b/c  9  =

Now you get the answer as a fraction. To change this to a decimal number, key in: a  b/c.

Finally round your answer to 3 decimal places.

​9​​7​​

Task 7:
Do the same with:
39

​51​​47​​

1. 93.922
2. 39,922
3. 92.229
4. 39.922

Task 8:
Calculate and round to whole numbers:

8842 x

​13​​5​​

1. 3400
2. 3401
3. 340.1
4. 34.1

Instruction A :

How to solve an equation and round the answer?

Example:

Solve this equation:

47c - 38 = -7 (place a card on 47c)

47c = 31

c = 

 c        0.660 

For this notation, see next slide! 

​47​​31​​

≈

N  Notation of an approximation:
Instruction B:

The solution 

is written as a decimal number as follows:                    0.660

This number is rounded to 3 decimal places. 

The symbol         means 'is approximately equal to' and indicates that it is a rounded number.

≈

​47​​31​​

​47​​31​​

≈

Task 9:
Solve and round the following equation on paper:
17 + 16x = 40
Round your answer to 3 decimal places.
Finally choose the right answer!

1. 1.44
2. 1.438
3. 1,44
4. 14.4

Explanation task 9:

Solve this equation:

17 + 16 x = 40

16 x = 23 

x =  

Rounded to three decimal places  x      1.438

​16​​23​​

≈

Task 10:
Solve the following equation on paper:
-9v + 19 = 32
Round your answer to three decimal places.
Use this sign, which means 'is approximately equal to':
Finally choose the right answer!

≈

1. 1.44
2. -1.444
3. -1.445
4. 1,444

Explanation Task 10:

a. -9v + 19 =32

-9v = 13

v = 

v      -1.444

≈

​−9​​13​​

HOMEWORK

From now on, some homework exercises appear.

If you keyed in the wrong answer, try again!

You have the choice between:

- doing extra basic exercises (purple circle), for the BLUE group (needing more help)

- doing more challenging exercises (yellow circle), for the GREEN and PURPLE group

  (ready for more complicated exercises)

- doing both types of exercises (purple and yellow circles),          

   but remember: do at least half of all exercises!

   Maybe you even do all of them.

Extra BASIC:
Task 11:
Calculate, using your calculator:
0.5 + (4.6 + 12.4 ) : 34 =

1. 2
2. 1
3. 0
4. 3

Etra Basic:
Task 12:
Calculate:
(24.9 - 12.5) x 8.8 - 10.4 =

1. 89.72
2. 98,72
3. 98.72
4. 97.72

Task 13:
Which numbers(s) cannot be written as a decimal number that has exactly the same meaning?

​4​​1​​

​3​​2​​

​6​​5​​

​5​​4​​

1. 2/3 only
2. 1/4 and 5/6
3. 5/6 and 4/5
4. 2/3 and 5/6

Task 14: Extra Basic: Calculate and round to 2 decimal places:
477 x

​7​​4​​

1. 272,57
2. 227.57
3. 272.57
4. 227.571

Task 15:
Solve this equation on paper.
Use the card method.
Round your answer to 3 decimal places.
Finally choose the right answer.

47c - 38 = -7

1. 0.660
2. 0.661
3. 0.659
4. 0,660

CHALLENGE:
Task 16:
Make an equation for the following information:

27 Players of a football club will be taken to their match.
5 Of them always travel with their coach in his car.
There is room for 3 players in each of the cars of the parents.
Call the number of parents n.
Which of the following equations is correct?

1. 27 = 4n + 5
2. 5n + 3 = 27
3. 5 + 3n = 27
4. 27 = 5n + 3

CHALLENGE:
Task 17:
Solve the equation from the previous slide:
5 + 3n = 27
So: calculate n, the number of parents.
This number has to be rounded sensibly!

1. n = 7.333
2. n = 7
3. n = 7 .3
4. n = 8

Extra Basic
Task 18:
Solve this equation on paper.
Round your answer to 3 decimal places.
Finally choose the right answer.
2388 = 2000x + 387

1. 1.0005
2. 1,002
3. 1.001
4. -1.001

Extra Basic:
Task 19:
Solve this equation on paper.
Finally key in the answer, rounded to 3 decimal places:
123 = 23e - 3

1. 5.47
2. 5.48
3. 5,48
4. 5.478

Dear boys and girls, this was the final 'extra exercise'.

There is one more 'challenge exercise' to come. 

Hope you learned a lot and enjoyd too!

CHALLENGE:
Task 20:
In 2008 a world record was set for the fastest journey around the world in a speed boat. It lasted 1663.82 hours.
Calculate this in days, hours and minutes. Round to whole minutes.

1. 99,829.2 minutes
2. 69 days, 7 hours and 49 minutes
3. 69 days, 7 hours and 53 minutes
4. 69 days, 7 hours and 54 minutes

Dear boys and girls, the task you've just been doing was the final homework exercise!

Hope you learned a lot and enjoyed!

Homework time

Do §10-4 The calculator now,

afterwards checking your results with the

Solutionbook.