Chapter 11

Chapter 11 (percentages)

                                     

In this chapter you will learn more about percentages.

11.1 Using mental method

Some percentages are easy to find because they are simple fractions. But some of them are hard to find because they are not always a simple fraction.

Example

Question

26% of 78 = 20.28

Use this fact to find:

    A)52% of $78 B) 13% of 78 kg C) 65% of 78 km

D) 104% of 78 million

Answer

    A) 20.28 × 2 = 40.56 B) 20.28 ÷ 2 = 10.14 C)

D) 20.28 × 4 = 81.14

Question

à Work out:

    A) 12.5% of 80  B) 0.5% of 7000 C) 150% of 62

D) 125% of 260 E) 110% of 36

à Work out:

    A) 35% of 84 B) 49% of 230 C) 77% of 4400

D) 99% of 7900 E) 45% of 56000

11.2 comparing different quantities

You will often need to compare groups that are different sizes.

Example

Question

This table shows the results of a survey in a factory.

	SMOKER	NON-SMOKER	TOTAL
MEN	12	64	76
WOMEN	9	32	41

    A) What percentage of men are smokers?

    B)  Compare the percentages of men and women who are non-smokers

Answer

A) 12/76 × 100% =  15,78 %

B)  Men : 64/76 × 100 % = 84,21 %

Women: 32/41 × 100% = 78,04 %

Question

 Ø There were 270 people in cinema. There were 168 women and 102 men.

There were 152 people in a theatre. There were 78 women and 74 men.

    A) Work out the percentage of women in each venue.

    B)  Work out the percentage of men in each venue.

Answer

    A) 113,3

    B)  86,3

11.3 percentages changes

You can use percentages to describe a change in a quantity. It could be an INCREASE or a DECREASE.

Question

 Ø The price of a car was $ 20.000. In a sale, the price decreased by 4%. After the sale it increased by 4%

A) What mistake has Ahmad made?

B)  What is the correct price after the sale?

Ahmad said” the price after the sale is % 20.000 again”

Answer

A)  Estimating the sale price

B)  4%4= 4/100 ×  $20 000 = 800

= 20 000 – 800 = 19 200

Price after sale = 4/100 x 19 200 = 768

                        = 19 200 + 768

11.4 Practical examples100 x $20 0

Profit: sell for more than you buy

Loss: sell for less than you buy

Discount: reduction in the price, it is usually given as a percentage

Interest: bank charges

Tax: if you buy something the price may include a additional price.

Examples

Question

 Ø A women bought an old chair for $240. She sold it for $ 300

Work out the percentages profit.

 Ø  A man bought a car for $ 15 900. He sold it for

$9500

Work out the percentages loss.

 Ø  A bottle of juice costs $ 6.50

If you buy six bottle you can get 10% discount.

Work out how much he sells them for.

Answer

 Ø  $ 300 - $ 240 = 60

60/240 x 100 % = 25 %

 Ø  15 900 – 9500 = 6400

6400/15900 x 100% = 40, 25 %

 Ø  6 x 6.5 = 39

Discount = 10/100 x 39 = 3, 9

After discount = 39 – 3, 9 = 35, 1

39-35, 1 = 3.9

00 = 800
         = 20 000 - 800 = 19.200

   price after sale = 4/100 x 19 200 = 768
                          = 19 200 + 7684% =>  4/100 x $20 000 = 800
         = 20 000 - 800 = 19.200

   price after sale = 4/100 x 19 200 = 768
                          = 19 200 + 7684% =>  4/100 x $20 000 = 800
         = 20 000 - 800 = 19.200

   price after sale = 4/100 x 19 200 = 768
                          = 19 200 + 7684% =>  4/100 x $20 000 = 800
         = 20 000 - 800 = 19.200

   price after sale = 4/100 x 19 200 = 768
                          = 19 200 + 7684% =>  4/100 x $20 000 = 800
         = 20 000 - 800 = 19.200

   price after sale = 4/100 x 19 200 = 768
               4% =>  4/100 x $20 000 = 800
         = 20 000 - 800 = 19.200

   price after sale = 4/100 x 19 200 = 768
                          = 19 200 + 768

Types of Topology

Bus

  Bus networks use a common backboneto connect all devices.the backbone function as a shared communication medium that devices attach or tap into with an interface connector.

  Ethernet bus topologies are relatively easy to install and don't require much cabling compared to the alternatives.

Ring

 

  in a ring network, every device has exactly two neighbours for communication purposes.

all messages travel through a ring in the same direction(either clockwise or counterclockwise).

  ring topologies are found in some office buildings or school campuses.

Star

  Many home networks use star topology.compared with bus topolgy,star require more cable.

computer network and mobile devices

Computer Network

computer network is a telecommunication network that allows computer to exchange data.the connections betweens nodes are established in using either cable media or wireless media.
the best known  network computer is internet.

en.wikipedia.org/wiki/Computer_network

mobile devices

mobile devices is a small and handled computing devices,typically having a display screen with a touch input or a miniature keyboard and weighing less than 2 pounds.
a handled computing device has an operating system and can run a various types of application software, known as apps.



en.wikipedia.org/wiki/Mobile_device

Chapter 10

10.1 calculating statistics

>  you can use statistics to summarise sets of data.

>  yo can also use them to compare different sets of data.

you should be able to calculate three different sets of data: the mode, the median, and the mean.

{ mode = most common value or number }

{ median = middle value *when they are listed in order }

{ mean = the sum of all the values divided by the number of values }

{ range = the largest value minus the smallest }

* is not an average

EXAMPLE

QUESTION

Number of beads/25 /30 /35 /40 /45 /50

frequency           /34 /48 /61 /30 /15 /12

the table shows the number of beads on 200 necklaces

A. find the mode

B. find the mean

C. find the range

ANSWER

A. the mode is 35 ( the mode is the number with the highest frequency)

B. 6900 : 200 = 34.5

C. 50 - 25 = 25

10.2 Using statistics

You have to decide which average to use to work out several different statistical measures.

choose mode --> if you want to know which is the most commonly occuring number.
median --> is the middle value, when the data values are put in order.
mean--> depends on every value, if you change one number you change the mean.

EXAMPLE

QUESTION

Here are the ages, in years, of the players in a football team.
work out the average age.give a reason for your choice of average.

16, 17, 18, 18, 19, 20, 20, 21, 21, 32, 41

ANSWER

The mode is not a good choice

the mean will be affected by the two oldest people.

the median is 20 and this is the best average to use in this case.

Are you trustworthy?

1. Suppose your best friend was in a fight, would you:

a). Help your friend by seperating them  and make them understand their problem against one another?

b) Walk away and pretend nothing actually happened?

C) Encourage your best friend to fight?

2. If you saw your friend struggle in a class test, would you:

a). Don't care cause it's his work anyways

b). Help him cheating and not feel guilty for it?

c). Call the teacher that your friend is in need of explainations?

3. If your friend told you a deep secret, would you:

a). Tell everyone the secret and turn your friend into a joke?

b). Keep it safe and make sure you don't speak of it one bit?

c). Tell your friend your deepest secret too?

4. If your friend has commited vandalism by accident, would you:

a). Tell the teacher directly that it wasn't an accident and make him take the punsihment alone?

b). Tell the teacher that it was also your fault and defend your friend?

c). Leave him?

5. If you and your friend went to a party and came home late then suddenly your friend's parents found out, would you:

a). Tell them that it was all your friend's idea?

b). Tell them that you insisted your friend to go?

c). Ignore them and walk away?