Shopping on line can be easy, simple and save you lots of money. It can also take a lot of your time, frustrate you, and result in unwanted purchases. Now the same can be said for regular high street shopping, but with the vast opportunity presented by the Internet it will pay you to spend a few minutes reading this and understanding how to better optimize your Percentage shopping experience:
1. Compare - without doubt the biggest advantage that the Percentage offers shoppers today is the ability to compare thousands of Percentage at a time. This is a great thing, but not necessarily all the time! Too much can be daunting at times so take advantage of the great comparison sites and where possible let them do the hard work for you.
2. Research - if it has been said it will be on the internet. Ignorance is no longer a justifiable reason for buying the wrong thing. Take the time to research in detail everything that you could possible want to know about
3. Testimonials - don't know anybody that has bought a Percentage? Wrong! If the Percentage is good the internet will let you know. Use the Internet as a friend and get testimonials before you buy.
4. Questions - Got a question about Percentage then search the Forums, FAQ's, Blogs etc. Don't be afraid to ask .....
5. Reputation - Never heard of the company selling Percentage? Don't worry, no reason why you should know every company in the world, but you know someone that does! Use the internet to find out what people are saying about Percentage and build up a picture of their reputation for sales, returns, customer service, delivery etc.
6. Returns - still worried that even after all of the above your Percentage wont be what you want? Check out the returns policy. There is so much competition now that someone, somewhere is bound to offer the terms that you are comfortable with.
7. Feedback - happy with your Percentage then let people know, after all you are depending on others people input in your buying decision, so why not give a little back.
8. Security - check for the yellow padlock on the Percentage site before you buy, and the s after http:/ /i.e. https:// = a secure site
9. Contact - got a question about Percentage, or want to leave a comment then check out the sites contact page. Reputable companies have them and respond.
10. Payment - ready to pay for your Percentage, then use your credit card or PayPal! Be aware of companies that don't accept them, there may be genuine reasons but given the huge amount of choice you have when buying online there is no reason at all not to buy via credit card or PayPal.
In mathematics, a
percentage is a way of expressing a number as a fraction of 100 (
per cent meaning "per hundred"). It is often denoted using the
percent sign, "%". For example, 45 % (read as "forty-five percent") is equal to 45 / 100, or 0.45.
Percentages are used to express how large one quantity is relative to another quantity. The first quantity usually represents a part of, or a change in, the second quantity. For example, an increase of $ 0.15 on a price of $ 2.50 is an increase by a fraction of 0.15 / 2.50 = 0.06. Expressed as a percentage, this is therefore a 6 % increase.
Although percentages are usually used to express numbers between zero and one, any
dimensionless Proportionality (mathematics) can be expressed as a percentage. For instance, 111 % is 1.11 and −0.35 % is −0.0035.
Proportions
Percentages are correctly used to express fractions of the total. For example, 25 % means 25 / 100 or "one quarter".
Percentages larger than 100 %, such as 101 % and 110 %, may be used as a literary paradox to express motivation and exceeding of expectations. For example, "We expect you to give 110 % your ability", however there are cases when percentages over 100 can be meant literally.
Calculations
The fundamental concept to remember when performing calculations with percentages is that the percent symbol can be treated as being equivalent to the pure number constant 1/100=0.01. For example, 35 % of 300 can be written as 35(0.01)(300)=105.
To find the percentage of a single unit in the whole, divide 100 by the whole. For instance, if you have 1250 apples, and you want to find out what percentage of the 1250 apples a single apple represents, 100 / 1250 would provide the answer of 0.08 %.
To calculate a percentage of a percentage, convert both percentages to fractions of 100, or to decimals, and multiply them. For example, 50 % of 40 % is:
(50/100)(40/100)=(0.50)(0.40)=0.20=20 %.
It is not correct to divide by 100 and use the percent sign at the same time. (E.g. 25% = 25/100 = 0.25, not 25%/100, which is actually (25/100)/100 = 0.0025.)
An example problem
Whenever we talk about a percentage, it is important to specify what it is relative to, i.e. what the total is that corresponds to 100 %. The following problem illustrates this point.
In a certain college 60 % of all students are female, and 10 % of all students are computer science majors. If 5 % of females are computer science majors, what percentage of computer science majors are female?
We are asked to compute the ratio of female computer science majors to all computer science majors. We know that 60 % of all students are female, and among these 5 % are computer science majors, so we conclude that .6 × .05 = .03 or 3 % of all students are female computer science majors. Dividing this by the 10 % of all students that are computer science majors, we arrive at the answer: 3 % / 10 % = .3 or 30 % of all computer science majors are female.
This example is closely related to the concept of
conditional probability.
Here are other examples:
1. What is 200 % of 30? Answer: X = 200% * 30, therefore X = (30 * 200 * 0.01) = 60
2. What is 13 % of 98? Answer: X = 13% * 98, therefore X = (98 * 13 * 0.01) = 12.74
3. 60 % of all university students are female. There are 2400 female students. How many students are in the university? Answer: 2400 = 60% * X, therefore X = (2400 / (60 * 0.01) ) = 4000
4. There are 300 cats in the village, and 75 of them are black. What is the percentage of black cats in that village? Answer: 75 = X% * 300, therefore X = (75 / 300 ) / 0.01 = 25 %
Percent increase and decrease
Due to inconsistent usage, it is not always clear from the context what a percentage is relative to. When speaking of a "10 % rise" or a "10 % fall" in a quantity, the usual interpretation is that this is relative to the
initial value of that quantity. For example, if an item is initially priced at $200 and the price rises 10 % (an increase of $20), the new price will be $220. Note that this final price is 110 % of the initial price (100 % + 10 % = 110 %).
Some other examples of percent change:
- An increase of 100 % in a quantity means that the final amount is 200 % of the initial amount (100 % of initial + 100 % of initial = 200 % of initial); in other words, the quantity has doubled.
- An increase of 800 % means the final amount is 9 times the original (100 % + 800 % = 900 % = 9 times as large).
- A decrease of 60 % means the final amount is 40 % of the original (100 % − 60 % = 40 %).
- A decrease of 100 % means the final amount is zero (100 % − 100 % = 0 %).
In general, a change of x percent in a quantity results in a final amount that is 100+x percent of the original amount (equivalently, 1+0.01x times the original amount).
It is important to understand that percent changes, as they have been discussed here,
do not add in the usual way. For example, if the 10 % increase in price considered earlier (on the $200 item, raising its price to $220) is followed by a 10 % decrease in the price (a decrease of $22), the final price will be $198,
not the original price of $200.
The reason for the apparent discrepancy is that the two percent changes (+10 % and −10 %) are measured relative to
different quantities ($200 and $220, respectively), and thus do not "cancel out".
In general, if an increase of x percent is followed by a decrease of x percent, the final amount is (1+0.01x)(1-0.01x)=1-(0.01x)^2 times the initial amount — thus the net change is an overall decrease by x percent
of x percent (the square of the original percent change when expressed as a decimal number).
Thus, in the above example, after an increase and decrease of x=10 percent, the final amount, $198, was 10 % of 10 %, or 1 %, less than the initial amount of $200.
In the case of
interest rates, it is a common practice to state the percent change differently. If an interest rate rises from 10 % to 15 %, for example, it is typical to say, "The interest rate increased by 5 %" — rather than by 50 %, which would be correct when measured as a percentage of the initial rate (i.e., from 0.10 to 0.15 is an increase of 50 %). Such ambiguity can be avoided by using the term "percentage points". In the previous example, the interest rate "increased by 5 percentage points" from 10 % to 15 %. If the rate then drops by 5 percentage points, it will return to the initial rate of 10 %, as expected.
Word and symbol
In
British English,
percent is usually written as two words (
per cent, although
percentage and
percentile are written as one word). In American English,
percent is the most common variant (but cf.
per mille written as two words).In EU context the word is always spelled out in one word
percent, despite the fact that they usually prefer British spelling, which may be an indication that the form is becoming prevalent in British spelling as well.In the early part of the
twentieth century, there was a dotted abbreviation form
"per cent.", as opposed to
"per cent". The form "per cent." is still in use as a part of the highly formal language found in certain documents like commercial loan agreements (particularly those subject to, or inspired by, common law), as well as in the
Hansard transcripts of British Parliamentary proceedings. While the term has been attributed to
Latin per centum, this is a Dog Latin construction and the term was likely originally adopted from
Italian language per cento or
French language pour cent. The concept of considering values as parts of a hundred is originally
Ancient Greece. The percent sign (%) evolved from a symbol abbreviating the Italian
per cento.
Grammar and style guides often differ as to how percentages are to be written. For instance, it is commonly suggested that the word percent (or per cent) be spelled out in all texts, as in "1 percent" and not "1 %." Other guides prefer the word to be written out in humanistic texts, but the symbol to be used in scientific texts. Most guides agree that they always be written with a numeral, as in "5 percent" and not "five percent," the only exception being at the beginning of a sentence: "Ninety percent of all writers hate style guides." Decimals are also to be used instead of fractions, as in "3.5 percent of the gain" and not "3 ½ percent of the gain." It is also widely accepted to use the percent symbol (%) in tabular and graphic material. Variations of practically all of these rules may be encountered, including in this article; the only really fast rule is to be consistent. It is important to know what method of solving the problem you would use.
In the
USA, fractions of 1 % are described in a verbose manner, e.g. "0.5 %" is usually referred to as "one half of one percent". In other countries, they are usually referred to in mathematical notation (in this case "zero point five percent"). This is due to differences in educational backgrounds.
English-speaking countries once did not put a typographic space before a percentage sign in any medium: handwritten, printed, typed, or in computer displays; the last of which can be seen in this article. This is historically a French practise and has become part of European Union and ISO regulations, but it will not be found in official documents, for example, prior to submission to the international regime.
Related units
External links
- percent-change.com percent change calculator
In
mathematics, a
percentage is a way of expressing a number as a fraction of 100 (
per cent meaning "per hundred"). It is often denoted using the percent sign, "%". For example, 45 % (read as "forty-five percent") is equal to 45 / 100, or 0.45.
Percentages are used to express how large one quantity is relative to another quantity. The first quantity usually represents a part of, or a change in, the second quantity. For example, an increase of $ 0.15 on a price of $ 2.50 is an increase by a fraction of 0.15 / 2.50 = 0.06. Expressed as a percentage, this is therefore a 6 % increase.
Although percentages are usually used to express numbers between zero and one, any
dimensionless Proportionality (mathematics) can be expressed as a percentage. For instance, 111 % is 1.11 and −0.35 % is −0.0035.
Proportions
Percentages are correctly used to express fractions of the total. For example, 25 % means 25 / 100 or "one quarter".
Percentages larger than 100 %, such as 101 % and 110 %, may be used as a literary paradox to express motivation and exceeding of expectations. For example, "We expect you to give 110 % your ability", however there are cases when percentages over 100 can be meant literally.
Calculations
The fundamental concept to remember when performing calculations with percentages is that the percent symbol can be treated as being equivalent to the pure number constant 1/100=0.01. For example, 35 % of 300 can be written as 35(0.01)(300)=105.
To find the percentage of a single unit in the whole, divide 100 by the whole. For instance, if you have 1250 apples, and you want to find out what percentage of the 1250 apples a single apple represents, 100 / 1250 would provide the answer of 0.08 %.
To calculate a percentage of a percentage, convert both percentages to fractions of 100, or to decimals, and multiply them. For example, 50 % of 40 % is:
(50/100)(40/100)=(0.50)(0.40)=0.20=20 %.
It is not correct to divide by 100 and use the percent sign at the same time. (E.g. 25% = 25/100 = 0.25, not 25%/100, which is actually (25/100)/100 = 0.0025.)
An example problem
Whenever we talk about a percentage, it is important to specify what it is relative to, i.e. what the total is that corresponds to 100 %. The following problem illustrates this point.
In a certain college 60 % of all students are female, and 10 % of all students are computer science majors. If 5 % of females are computer science majors, what percentage of computer science majors are female?
We are asked to compute the ratio of female computer science majors to all computer science majors. We know that 60 % of all students are female, and among these 5 % are computer science majors, so we conclude that .6 × .05 = .03 or 3 % of all students are female computer science majors. Dividing this by the 10 % of all students that are computer science majors, we arrive at the answer: 3 % / 10 % = .3 or 30 % of all computer science majors are female.
This example is closely related to the concept of conditional probability.
Here are other examples:
1. What is 200 % of 30? Answer: X = 200% * 30, therefore X = (30 * 200 * 0.01) = 60
2. What is 13 % of 98? Answer: X = 13% * 98, therefore X = (98 * 13 * 0.01) = 12.74
3. 60 % of all university students are female. There are 2400 female students. How many students are in the university? Answer: 2400 = 60% * X, therefore X = (2400 / (60 * 0.01) ) = 4000
4. There are 300 cats in the village, and 75 of them are black. What is the percentage of black cats in that village? Answer: 75 = X% * 300, therefore X = (75 / 300 ) / 0.01 = 25 %
Percent increase and decrease
Due to inconsistent usage, it is not always clear from the context what a percentage is relative to. When speaking of a "10 % rise" or a "10 % fall" in a quantity, the usual interpretation is that this is relative to the
initial value of that quantity. For example, if an item is initially priced at $200 and the price rises 10 % (an increase of $20), the new price will be $220. Note that this final price is 110 % of the initial price (100 % + 10 % = 110 %).
Some other examples of percent change:
- An increase of 100 % in a quantity means that the final amount is 200 % of the initial amount (100 % of initial + 100 % of initial = 200 % of initial); in other words, the quantity has doubled.
- An increase of 800 % means the final amount is 9 times the original (100 % + 800 % = 900 % = 9 times as large).
- A decrease of 60 % means the final amount is 40 % of the original (100 % − 60 % = 40 %).
- A decrease of 100 % means the final amount is zero (100 % − 100 % = 0 %).
In general, a change of x percent in a quantity results in a final amount that is 100+x percent of the original amount (equivalently, 1+0.01x times the original amount).
It is important to understand that percent changes, as they have been discussed here,
do not add in the usual way. For example, if the 10 % increase in price considered earlier (on the $200 item, raising its price to $220) is followed by a 10 % decrease in the price (a decrease of $22), the final price will be $198,
not the original price of $200.
The reason for the apparent discrepancy is that the two percent changes (+10 % and −10 %) are measured relative to
different quantities ($200 and $220, respectively), and thus do not "cancel out".
In general, if an increase of x percent is followed by a decrease of x percent, the final amount is (1+0.01x)(1-0.01x)=1-(0.01x)^2 times the initial amount — thus the net change is an overall decrease by x percent
of x percent (the square of the original percent change when expressed as a decimal number).
Thus, in the above example, after an increase and decrease of x=10 percent, the final amount, $198, was 10 % of 10 %, or 1 %, less than the initial amount of $200.
In the case of
interest rates, it is a common practice to state the percent change differently. If an interest rate rises from 10 % to 15 %, for example, it is typical to say, "The interest rate increased by 5 %" — rather than by 50 %, which would be correct when measured as a percentage of the initial rate (i.e., from 0.10 to 0.15 is an increase of 50 %). Such ambiguity can be avoided by using the term "
percentage points". In the previous example, the interest rate "increased by 5 percentage points" from 10 % to 15 %. If the rate then drops by 5 percentage points, it will return to the initial rate of 10 %, as expected.
Word and symbol
In British English,
percent is usually written as two words (
per cent, although
percentage and
percentile are written as one word). In
American English,
percent is the most common variant (but cf.
per mille written as two words).In EU context the word is always spelled out in one word
percent, despite the fact that they usually prefer British spelling, which may be an indication that the form is becoming prevalent in British spelling as well.In the early part of the twentieth century, there was a dotted abbreviation form
"per cent.", as opposed to
"per cent". The form "per cent." is still in use as a part of the highly formal language found in certain documents like commercial loan agreements (particularly those subject to, or inspired by, common law), as well as in the
Hansard transcripts of British Parliamentary proceedings. While the term has been attributed to
Latin per centum, this is a
Dog Latin construction and the term was likely originally adopted from
Italian language per cento or French language
pour cent. The concept of considering values as parts of a hundred is originally
Ancient Greece. The
percent sign (%) evolved from a symbol abbreviating the Italian
per cento.
Grammar and style guides often differ as to how percentages are to be written. For instance, it is commonly suggested that the word percent (or per cent) be spelled out in all texts, as in "1 percent" and not "1 %." Other guides prefer the word to be written out in humanistic texts, but the symbol to be used in scientific texts. Most guides agree that they always be written with a numeral, as in "5 percent" and not "five percent," the only exception being at the beginning of a sentence: "Ninety percent of all writers hate style guides." Decimals are also to be used instead of fractions, as in "3.5 percent of the gain" and not "3 ½ percent of the gain." It is also widely accepted to use the percent symbol (%) in tabular and graphic material. Variations of practically all of these rules may be encountered, including in this article; the only really fast rule is to be consistent. It is important to know what method of solving the problem you would use.
In the
USA, fractions of 1 % are described in a verbose manner, e.g. "0.5 %" is usually referred to as "one half of one percent". In other countries, they are usually referred to in mathematical notation (in this case "zero point five percent"). This is due to differences in educational backgrounds.
English-speaking countries once did not put a typographic space before a percentage sign in any medium: handwritten, printed, typed, or in computer displays; the last of which can be seen in this article. This is historically a French practise and has become part of European Union and
ISO regulations, but it will not be found in official documents, for example, prior to submission to the international regime.
Related units
External links
- percent-change.com percent change calculator
GCSE MATHS: Percentage Difference
Tutorials, tips and advice on GCSE Maths coursework and exams for students, parents and teachers.
GCSE MATHS: Percentage
Tutorials, tips and advice on GCSE Maths coursework and exams for students, parents and teachers.
Body Fat Percentage
Complete your food diary every day, stay within your calorie allowance and you WILL lose weight. or your money back.
Percentage - Wikipedia, the free encyclopedia
In mathematics, a percentage is a way of expressing a number as a fraction of 100 (per cent meaning "per hundred"). It is often denoted using the percent sign,
BBC - Skillswise % increase and decrease
Factsheets and worksheets for work on finding percentage increases and decreases. ... If you want a reminder of how percentages work look at the module called Introduction to
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