ALEXANDER PENUELA
RAFAEL PEDRAZA RUIZ
SANTIAGO HUERTAS
SERGIO RIOS
FELIPE BARCHA
4-A

To understand decimal numbers you must first know about
Place Value .
When we write numbers, the
position (or "place") of each number is important.
In the number 327: the "7" is in the Units position, meaning just 7 (or 7 "1"s), the "2" is in the Tens position meaning 2 tens (or twenty), and the "3" is in the Hundreds position, meaning 3 hundreds.
" Three Hundred Twenty Seven "

As we move left, each position is 10 times bigger!
From Units, to Tens, to Hundreds
... and ...
As we move right, each position is 10 times smaller.
From Hundreds, to Tens, to Units
But what if we continue past Units?
What is 10 times smaller than Units?
1 /
10 ths (Tenths) are!

But we must first write a decimal
point, so we know exactly where the
Units position is:
"three hundred twenty seven and four tenths"

The zero and the counting numbers (1,2,3,...) make up the set of whole numbers. But not every number is a whole number. Our decimal system lets us write numbers of all types and sizes, using a clever symbol called the decimal point.
As you move right from the decimal point, each place value is divided by 10.
1 2 7 . 8 5 4
Hundreds thousandths tens hundredths ones tenths

The decimal number can be represented by square or large rectangles.
3
10
= 0.3

There are three different types of decimal number: exact, recurring and other decimals.
An exact or terminating decimal is one which does not go on forever, so you can write down all its digits. For example: 0.125
A recurring decimal is a decimal number which does go on forever, but where some of the digits are repeated over and over again.
For example: 0.1252525252525252525... is a recurring decimal, where '25' is repeated forever.
Other decimals are those which go on forever and don't have digits which repeat. For example pi =
3.141592653589793238462643...

FRACTION
58/100
Example 1 : If 58 out of 100 students in a school are boys, then write a decimal for the part of the school that consists of boys.
Analysis: We can write a fraction and a decimal for the part of the school that consists of boys
DECIMAL
0.58

Example 3:
Example 2:
Five swimmers are entered into a competition.
Four of the swimmers have had their turns. Their scores are 9.8 s, 9.75 s, 9.79 s, and 9.81 s.
What score must the last swimmer get in order to win the competition?
Analysis: We must order these decimals from least to greatest. Then we must determine how the least compares with the winning score.
Step 1: 9 . 75
9 . 79
9 . 80
9 . 81
Step 2: The least decimal is 9.75. Now we must determine how 9.75 compares with the winning score.
Answer: The last swimmer must get a score less than 9.75 s in order to win.

1. Example 3 : Ellen wanted to buy the following items: A DVD player for $49.95, a DVD holder for $19.95 and a personal stereo for $21.95. Does Ellen have enough money to buy all three items if she has $90 with her?
Analysis: The phrase enough money tells us that we need to estimate the sum of the three items. We will estimate the sum by rounding each decimal to the nearest one. We must then compare our estimated sum with $90 to see if she has enough money to buy these items.
$49.95
$19.95
$21.95
$50.00
$20.00
$22.00
$92.00
Answer: No, because rounding each decimal to the nearest one, we get an estimate of $92, and Ellen only has
$90 with her.

In the 1968 Summer Olympics, Irena Szewinska of
Poland won the women´s 200 meters dash with a time of 22.5 seconds,. In 1996, Marie-Jose Perec of France won the event with a time of 22.12 seconds. Whose time is faster?
Hundred thousand
Ten thousans
Thousans Hundred s
Tens Ones Tenths Hundredths Thousandths Tenthousandths
2 2.
5
2 2.
1 2

The tens´and ones´digits are
22.50
22.12
The tenths´digits are different.
5 > 1, so 22.50 > 22.12

Central Park, in Manhattan, New York, is one of the world´s most famous parks. If you walked around the entire perimeter of the 2.5 mile by 0.5 mile park, how far would you walk?

0.5 mile wide
2.5 mile long
Solution :
A = lw Write formula for area of
= 2.5 (0.5) Substitute 2.5 for l and 0.5 for w.
= 1.25 Multiply.

Ticket prices: The cost of 21 tickets to see Blue Man
Group is $761.25 . How much does each ticket?
You can use long division to divide a decimal by a whole number. Divide as with whole numbers. Then line up the decimal points in the quotient and the dividend.

Solution: Dividing a decimal by a Whole Number
36.25
21 ) 761.25
63
131
126
52
42
105
105
0

Longest Submarine Sandwich: In 1979, Chef Franz
Eichenauer made a submarine sandwich that was
322.5 meters long. Suppose the sandwich was cut into pieces each measured 25.8 centimeters. How many would there be?

Solution:
1. Convert 322.5 meters to centimeters by multipliying by 100.
322.5 x 100 = 32,250 so 322.5 m = 32,250 cm
2. To find the number of pieces, divide the total length of the sandwich by the length of each piece.
32,250 cm ÷ 25.8 cm = 1.250