Decimals, Fractions, and Percents
Decimals, Fractions and Percentages
http://www.mathsisfun.com/decimal-fraction-percentage.html
8.17.2011
Decimals, Fractions and
Percentages are just different ways of showing the same value:
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Example
Values
Here is a table of commonly
occuring values shown in Percent, Decimal and
Fraction form:
|
Percent |
Decimal |
Fraction |
|
1% |
0.01 |
1/100 |
|
5% |
0.05 |
1/20 |
|
10% |
0.1 |
1/10 |
|
12½% |
0.125 |
1/8 |
|
20% |
0.2 |
1/5 |
|
25% |
0.25 |
1/4 |
|
331/3% |
0.333... |
1/3 |
|
50% |
0.5 |
1/2 |
|
75% |
0.75 |
3/4 |
|
80% |
0.8 |
4/5 |
|
90% |
0.9 |
9/10 |
|
99% |
0.99 |
99/100 |
|
100% |
1 |
|
|
125% |
1.25 |
5/4 |
|
150% |
1.5 |
3/2 |
|
200% |
2 |
Conversions
From
Percent to Decimal
To convert from percent to decimal: divide by 100, and remove
the "%" sign.
The easiest way to divide
by 100 is to move the
decimal point 2 places to the left. So:
|
From Percent |
To
Decimal |
|
|
|
move the decimal point 2 places to the
left, and remove the "%" sign. |
|
From
Decimal to Percent
To convert from decimal to percent: multiply by 100, and add
a "%" sign.
The easiest way to multiply
by 100 is to move the
decimal point 2 places to the right. So:
|
From Decimal |
To Percent |
|
|
|
move the decimal point 2 places to the
right, and add the "%" sign. |
|
From
Fraction to Decimal
The easiest way to convert a fraction to a decimal is to
divide the top number by the bottom number (divide the numerator by the
denominator in mathematical language)
Example: Convert 2/5 to a
decimal
Divide 2
by 5: 2 ÷ 5 = 0.4
Answer: 2/5 = 0.4
From
Decimal to Fraction
To convert a decimal to a fraction needs a
little more work.
Example: To convert 0.75 to a fraction
|
Steps |
Example |
|
First, write down the decimal
"over" the number 1 |
0.75 / 1 |
|
|
|
|
Then multiply top and bottom by 10
for every number after the decimal point (10 for 1 number, 100 for 2 numbers,
etc) |
0.75
× 100 / 1 × 100 |
|
(This makes it a correctly formed
fraction) |
= 75 / 100 |
|
Then Simplify the fraction |
3 / 4 |
From
Fraction to Percentage
The easiest way to convert a fraction to a percentage is to divide the top number by the bottom number. then multiply the result by 100, and add the "%"
sign.
Example: Convert 3/8 to a
percentage
First
divide 3 by 8: 3 ÷ 8 = 0.375,
Then multiply by 100: 0.375 x 100 = 37.5
Add the "%" sign: 37.5%
Answer: 3/8 = 37.5%
From
Percentage to Fraction
To convert a percentage to a fraction, first
convert to a decimal (divide by 100), then use the steps for converting decimal
to fractions (like above).
Example: To convert 80% to a fraction
|
Steps |
Example |
|
Convert 80% to a decimal
(=80/100): |
0.8 |
|
Write down the decimal
"over" the number 1 |
0.8 / 1 |
|
|
|
|
Then multiply top and bottom by 10
for every number after the decimal point (10 for 1 number, 100 for 2 numbers,
etc) |
0.8 ×
10 / 1 × 10 |
|
(This makes it a correctly formed
fraction) |
= 8 / 10 |
|
Then Simplify the fraction |
4 / 5 |
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