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How to Find 20 Percent of a Number

How to Find 20 Percent of a Number

How to Find 20 Percent of a Number

Ah, math. It's one of the most enduring mysteries of ALL time. And as much as you would absolutely love to have one doozy of a homework assignment — you can't.

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After a delicious lunch, there's a time for a cup of coffee. It may sound quite weird for you, what do coffee and percentage have in common? Our coffee kick calculator tells you what your level of alertness is in percentages during the day! Check out how a dose of caffeine helps you remain focused! Also, if you're a real coffee-lover, try our other tools. With coffee to water ratio calculator, you can find a perfect ratio of ingredients to prepare your cup of coffee and caffeine calculator shows you how much caffeine you've had during a day. Be aware that you can overdose on caffeine too! Percentage points (or percent points) are a rather tricky beast. We use it all the time even if we don't know it - and in these situations, we often incorrectly say percent instead of a percentage point. Once you read this section, you will know how to do it properly and be annoyed for the rest of your life (because other people will keep making the mistake). We can already say that percentage points play an essential role in statistics, e.g., in the normal distribution, binomial distribution, or to find the confidence interval for a sample of data (confidence level is usually at 95 percentage points).

Let's give ourselves a little bit of practice with percentages. So let's ask ourselves, what percent of-- I don't know, let's say what percent of 16 is 4? And I encourage you to pause this video and to try it out yourself. So when you're saying what percent of 16 is 4, percent is another way of saying, what fraction of 16 is 4? And we just need to write it as a percent, as per 100. So if you said what fraction of 16 is 4, you would say, well, look, this is the same thing as 4/16, which is the same thing as 1/4. But this is saying what fraction 4 is of 16. You'd say, well, 4 is 1/4 of 16. But that still doesn't answer our question. What percent? So in order to write this as a percent, we literally have to write it as something over 100. Percent literally means "per cent." The word "cent" you know from cents and century. It relates to the number 100. So it's per 100. So you could say, well, this is going to be equal to question mark over 100, the part of 100. And there's a bunch of ways that you could think about this. You could say, well, look, if in the denominator to go from 4 to 100, I have to multiply by 25. In the numerator to go from-- I need to also multiply by 25 in order to have an equivalent fraction. So I'm also going to multiply by 25. So 1/4 is the same thing as 25/100. And another way of saying 25/100 is this is 25 per 100, or 25%. So this is equal to 25%. Now, there's a couple of other ways you could have thought about it. You could have said well, 4/16, this is literally 4 divided by 16. Well, let me just do the division and convert to a decimal, which is very easy to convert to a percentage. So let's try to actually do this division right over here. So we're going to literally divide 4 by 16. Now, 16 goes into 4 zero times. 0 times 16 is 0. You subtract, and you get a 4. And we're not satisfied just having this remainder. We want to keep adding zeroes to get a decimal answer right over here. So let's put a decimal right over here. We're going into the tenths place. And let's throw some zeroes right over here. The decimal makes sure we keep track of the fact that we are now in the tenths, and in the hundredths, and in the thousandths place if we have to go that far. But let's bring another 0 down. 16 goes into 40 two times. 2 times 16 is 32. If you subtract, you get 8. And you could bring down another 0. And we have 16 goes into 80. Let's see, 16 goes into 80 five times. 5 times 16 is 80. You subtract, you have no remainder, and you're done. 4/16 is the same thing as 0.25. Now, 0.25 is the same thing as twenty-five hundredths. Or, this is the same thing as 25/100, which is the same thing as 25%. (Source: www.khanacademy.org)

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Let's give ourselves a little bit of practice with percentages. So let's ask ourselves, what percent of-- I don't know, let's say what percent of 16 is 4? And I encourage you to pause this video and to try it out yourself. So when you're saying what percent of 16 is 4, percent is another way of saying, what fraction of 16 is 4? And we just need to write it as a percent, as per 100. So if you said what fraction of 16 is 4, you would say, well, look, this is the same thing as 4/16, which is the same thing as 1/4. But this is saying what fraction 4 is of 16. You'd say, well, 4 is 1/4 of 16. But that still doesn't answer our question. What percent? So in order to write this as a percent, we literally have to write it as something over 100. Percent literally means "per cent." The word "cent" you know from cents and century. It relates to the number 100. So it's per 100. So you could say, well, this is going to be equal to question mark over 100, the part of 100. And there's a bunch of ways that you could think about this. You could say, well, look, if in the denominator to go from 4 to 100, I have to multiply by 25. In the numerator to go from-- I need to also multiply by 25 in order to have an equivalent fraction. So I'm also going to multiply by 25. So 1/4 is the same thing as 25/100. And another way of saying 25/100 is this is 25 per 100, or 25%. So this is equal to 25%. Now, there's a couple of other ways you could have thought about it. You could have said well, 4/16, this is literally 4 divided by 16. Well, let me just do the division and convert to a decimal, which is very easy to convert to a percentage. So let's try to actually do this division right over here. So we're going to literally divide 4 by 16. Now, 16 goes into 4 zero times. 0 times 16 is 0. You subtract, and you get a 4. And we're not satisfied just having this remainder. We want to keep adding zeroes to get a decimal answer right over here. So let's put a decimal right over here. We're going into the tenths place. And let's throw some zeroes right over here. The decimal makes sure we keep track of the fact that we are now in the tenths, and in the hundredths, and in the thousandths place if we have to go that far. But let's bring another 0 down. 16 goes into 40 two times. 2 times 16 is 32. If you subtract, you get 8. And you could bring down another 0. And we have 16 goes into 80. Let's see, 16 goes into 80 five times. 5 times 16 is 80. You subtract, you have no remainder, and you're done. 4/16 is the same thing as 0.25. Now, 0.25 is the same thing as twenty-five hundredths. Or, this is the same thing as 25/100, which is the same thing as 25%.

You can repeat these steps with multiple calculations for problems that have percentages that are not simple fractions. For example, when calculating the tip on a bill at a restaurant, you may be trying to find 15 percent of $27. Rather than converting 15 percent to 15/100 or 3/20, you can think of it as 10/100 or 1/10 and then add half of that, because it is much easier to find 1/10 than 3/20. So you would calculate 1/10 of $27, which is $2.70, plus half of that, or $1.35, to get a tip of $3.05. If you've ever bought clothes on sale, you're familiar with the concept of a markdown, or reducing the price by a given percentage. A markup works the opposite way: The price is ​increased​ by a given percentage. Retailers do this every day, because they pay one price for their goods (the wholesale price), and then add a markup to create the retail price they sell to you at. Often, the markup from wholesale price to retail price can be as much as 50 percent, but some retailers will sell at lower markups such as 20 percent. (Source: sciencing.com)

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If you've ever bought clothes on sale, you're familiar with the concept of a markdown, or reducing the price by a given percentage. A markup works the opposite way: The price is ​increased​ by a given percentage. Retailers do this every day, because they pay one price for their goods (the wholesale price), and then add a markup to create the retail price they sell to you at. Often, the markup from wholesale price to retail price can be as much as 50 percent, but some retailers will sell at lower markups such as 20 percent.Percentage increase and decrease are calculated by computing the difference between two values and comparing that difference to the initial value. Mathematically, this involves using the absolute value of the difference between two values, and dividing the result by the initial value, essentially calculating how much the initial value has changed.

The percentage increase calculator above computes an increase or decrease of a specific percentage of the input number. It basically involves converting a percent into its decimal equivalent, and either subtracting (decrease) or adding (increase) the decimal equivalent from and to 1, respectively. Multiplying the original number by this value will result in either an increase or decrease of the number by the given percent. Refer to the example below for clarification An example of a price/percentage increase is as follows: A TV cost $100 last year but now costs $125. To determine the price increase, you would subtract the old price from the new price: 125 - 100 = 25. You would then divide this by the old price: 25 divide by 100 equals 0.25. You will then multiply this number by 100: 0.25 x 100 = 25, or 25%. So, the TV price has increased by 25% over the past year. (Source: www.indeed.com)

 

 

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