Fifteen percent of 200 is 30. You can compute a percent very simply and effectively utilizing a couple of different techniques. The most widely recognized method of calculating percentages is to divide the smaller number by the bigger number and afterward multiply by the value by 100.

As an example, to determine what percentage of 24 the number 8 is, you’ll want to divide the 8 by 24 and then multiply by 100, which gives you the number 33.3 percent. We’ll find out how to use this basic concept of percentages to find 15% of 200 below.


While researchers often need to use percentages to determine the probability or to determine the particular gravity of a collection of atoms, nearly everybody needs to compute a percentage at some point during the week. You may have to determine a percentage to know how much to tip, how much you’ll pay in taxes, or determine the probability of something. For these reasons, knowing how to quickly ascertain percentages is an excellent skill to have.

Let’s examine some of the different ways to calculate percentages.

How To Calculate A Percentage

The primary way to calculate percentages is to take the smaller number and divided by the larger number. For instance, if you have the number 386, and you need to determine what percentage of 386 239 is, you just need to divide 239 by 386. This turns out to be 0.6191. To convert 0.6111 into a percentage, you can simply move the decimal point to the right by two columns. After you’ve done this, you’ll have the percentage 61.9%. Note that you can carry out this process in reverse as well. If you need a decimal from a percentage, you can just move the decimal point over to the left by two columns.


Meanwhile, if you have a percentage and the need to convert this percentage to a regular number, this can be done by making of the percentage a decimal, then multiplying the other number by the value of the decimal. Let’s take a look at a concrete example. For instance, if you need to determine a loan’s interest, and you know that the interest rate is 5% and that the loan was for the amount of $1500, you can start by converting 5% to 0.05. Now, all you have to do is multiply 1500 by the decimal and get 75. Just add 75 to 1500 to get 1575.

In the above example, we already knew the relevant percentage, but what if you are trying to find an unknown number that is a percentage of a different number? In this case, you’d want to to take your target percentage and multiply by the number you want to find the percentage of. If you are trying to save up enough money to go on a trip in a few months and you want to save 30% out of each paycheck you get, you’d want to use the decimal 0.30 and multiply it by your paycheck’s value. If your paycheck was 500 for the week, you know you’d want to save 150 out of it.

If the goal was to determine a rate of change between two different numbers, a percentage of change, you start by finding out what the difference in value between the two numbers is. For instance, if the cost of a TV has decreased from 200 down to 175, that’s a change of $25 in price. You can then divide 25 by 200 to get 0.125, or 12.5% So, in this case, the TV has dropped by 12.5% in price.


Solving For An Unknown Variable With Algebra

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To find the value of an unknown number that is some percentage of another number, we’ll need to do a bit of algebra.

So to find 15% of 200, start off by assuming that 200 is equal to 100% (since it is the whole number). Now we need to find 15% of 200, and we know that 200 = 100% while X = 15%. We need to isolate the X and the 15% from these two equations, so we can do something like this:

200/x = 100%/15%

Now we just need to resolve this equation.

(200/x)*x = (100/15)*x

Multiply both sides of the equation by X to get: 200 = 6.666*x

Now we divide both sides of this equation by 6.666 to get:

200/6.666 = X

Now we just resolve 200 divided by 6.666 to get approximately:

X = 30

Make Problems Simpler With Chunking

If you are struggling with determining percentages, or want a method to more reliably determine a percentage through mental math, you can do this through the process of chunking. Chunking is just dividing a more complex problem into smaller chunks, which are easier to work with. For example, if you were asked to find 60% of 48, start by finding half of 48, because 50% is just half. Half of 48 is 24, and 10% of 48 is 4.8, so now just combined 24 and 4.8’s to get 28.8.

Let’s look at a couple other examples.

If you’re trying to find 15% of the number 36, first find 10% of 36, which is 3.6. 5% is half of 10%, so just find half of 3.6, which ends up being 1.8. Now you can add 1.8 to 3.6 and come up with 5.4, which is indeed 15% of 36.

Here’s one final example, let’s say you are asked to find 85% of 72. Start by subtracting 15% from the number 72, since 85% is only 15% less than the entire value. 10% of 72 with 7.2, and 5% of 7.2 with 3.6. Now add 7.2 and 3.6 together to get 10.8. Since 10.8 is 15% of 72, subtract 10.8 from it to get 61.2, which is 85%.

Use Percentages To Estimate Probability

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Percentages are also critical to determining the probability of an event. Estimating probability is something that people try to do at some point almost every single day, but in general, people are not good with determining probability and frequently make mistakes. You can make determining probability easier by expressing something numerically in the form of a percentage, it just is a little more work to find a percentage.

The first step in estimating probabilities determining the number of variables you have to track. The number of variables that needs to be accounted for in your estimate depends on the number of possible results in the event being observed. When flipping a coin, there are only two possible results, heads or tails (we are ignoring the possibility of a coin standing on its side). This makes the probability very easy to determine, as there will always be half a chance of that tails or heads comes up on the coin, so a 50% probability of it landing on either side.

The odds of rolling any given number on a six-sided die or also easy to determine and the probability will be the same on every side. There are six different possible results and only one “goal” state. This means there will only ever be a one in six chance of it landing on your desired side. Just divide one by the number six to get around 16.6% or, expressed as a decimal 0.166.

Keep in mind that when calculating probabilities you need to determine whether or not the outcomes of the events are dependent or independent. Independent events are those have an outcome impact by the previous outcome, while independent events are those where a prior event doesn’t impact the outcome of the next event. For instance, drawing a card from a deck initially has a 1 in 52 chance of happening, but if the card is not replaced then the chance of drawing another card is only 1 in 51. This is a dependent event. Meanwhile, the probability of rolling any number on a die will always be ⅙, they are independent events.

To Sum Up:

To convert a decimal to a percentage, you can simply move the decimal point to the right by two columns. When you are calculating percentages, you can just divide the larger number into the smaller number or break the numbers up into smaller chunks to make it easier. This is handy when calculating probability.

About The Author

Daniel obtained his BS and is pursuing a Master's degree in the science of Human-Computer Interaction. He hopes to work on projects which bridge the sciences and humanities. His background in education and training is diverse including education in computer science, communication theory, psychology, and philosophy. He aims to create content that educates, persuades, entertains and inspires.