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Decimals are
also use to name numbers between
whole numbers.
Decimals are
the same as Fractions with
denominators that are multiples
of 10.
5 tenths =
5/10 = 0.5
5 hundredths
= 5/100 = 0.05
5
thousandths = 5/1,000 = 0.005
125
thousandths = 125/1,000 = 0.125
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Place positions of
decimals |
|
1000s
thousands |
100s
hundreds |
10s
tens |
1s
ones |
. |
0.1s
tenths |
0.01s
hundredths |
0.001s
thousandths |
|
|
2 |
4 |
6 |
. |
8 |
5 |
2 |
|
|
|
|
|
|
|
|
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The first
position to the right of the
decimal point represents tenths
– which is one divided into 10
parts.
The second
position to the right of the
decimal point represents
hundredths – which is one
divided into 100 parts.
The third
position is thousandths – which
is one divided into 1,000 parts.
The number
on the third line is:
Words – two
hundred forty six point eight
five two
Decimal
notation: 246.852
Fraction
notation: 246 852/1000, or 246
and 852 thousandths
A special
use for decimals is how we write
money numbers. We count money in
dollars and cents. We use the
symbol ‘$’ in front of the money
decimal number.
We write the
dollars as whole numbers, and
the cents as a decimal number.
The decimal point comes after
the whole number. The cents are
really hundredths of a dollar.
If a
cheeseburger costs 3 dollars and
99 cents, we would write:
$ 3.99
This means 3
dollars and 99 hundredths of
another dollar.
|
Comparing Decimal
Numbers |
Here are some
examples of decimal numbers that
are equal:
0.4 = 0.40 =
0.400 ( 4 tenths = 40 hundredths
= 400 thousandths)
0.25 = 0.250
= 0.2500 ( 25 hundredths = 250
thousandths = 2500
ten-thousandths)
When
comparing decimal numbers, it
helps to add zeroes to the right
of the last digit so that the
decimal numbers you are
comparing have the same number
of digits to the right of the
decimal point.
For example,
compare 0.4 with 0.060
First change
the 0.4 to 0.400
Now we can
compare 0.400 and 0.060
0.400 > 0.060
since 400 is > 60
Compare 0.205
with 0. 21
First change
0.21 to 0.210
Now we can
see that 0.205 < 0.210 since 205
< 210
|
Adding and Subtracting
Decimals |
You add and
subtract decimal numbers the
same way you add and subtract
whole numbers with one
additional rule:
|
Always line up the
decimal points of the
numbers so that the
decimal points are in
the same column. This
ensures that you are
adding numbers with the
same place value.
Sometimes, it is helpful
to add zeroes to the end
of a number so that all
numbers have the same
number of digits to the
right of the decimal
point. |
Example: Add
3.4 + 28.76 + 0.001
|
|
3 |
. |
4 |
0 |
0 |
|
2 |
8 |
. |
7 |
6 |
0 |
|
|
0 |
. |
0 |
0 |
1 |
|
3 |
2 |
. |
1 |
6 |
1 |
Remember:
You need to write your numbers
neatly!!!
|
Adding and Subtracting
Money |
You add or
subtract money numbers the same
way you add and subtract
decimals. Make sure you line up
the decimal points neatly.
$ 235.56
-$ 55.45
$ 180.11
0.75 is read
as 75 hundredths. So if 1 is
divided into 100 parts, 0.75
means 75 of those one hundredth
parts.
0.60 is read
as 60 hundredths. Again, if one
is divided into 100 parts, 0.60
means 60 of those hundredth
parts.
Percent means
per hundred or out of a hundred.
75% means 75 out of 100.
60% means 60
out of 100.
¾ = 0.75 =
75/100 = 75%
3/5 = 0.60 =
60/100 = 60%
½ = 0.50 =
50/100 = 50%
0.93 =
93/100 = 93% |
