# How to calculate percentages?-Tips and Exercises

**How to calculate percentages**

The percentage is applied on a daily basis and every day we see in the shops advertisements with sales of 20%, 30% or even 50% off.

But how do you quickly apply these discounts without complicating things too much? One of the quickest ways is with these simple examples.

"Take 10% off all orders of $99 and more" "Save 20% on your purchase of $100 or more!"

*Mathematics knows neither race nor geographical boundaries. For mathematics, the cultural world is a country. David Hilbert.*

**How to calculate the percentage of a final price?**

Step 1: Take the final price and divide it by the original price.

2000/1000=2

Step 2: Multiply the result by 100 to get the percentage.

2*100=200%

Knowing how to develop the percentage technique is the solution. Percentages or percentages are easy to calculate, although at first glance they may appear to be the opposite.

Percentages are calculated using the following equation: percentage = 100 x percentage / total 100 % equals 1, so a percentage could be 0.1 (10 %) or 10.739795714285.

To calculate percentages, simply divide the number of items by the total of all items. For example, if there are 10 widgets in a row and there are 100 pieces in a box, then 10% of 100 is 10.

**It will not be necessary to learn a formula, it is possible to calculate it through the rule of 3.**

**Example 1:**

Let's start with a very simple example of calculation.

If you have 30 colours, of which 7 are red, **what is the percentage of red colours that exist?**

- 7 Colours are Red
- 30 Is the total of the colours
- 100% Is the Total
- 30 COLOURS = 100%.
- 7 (RED) = x (this would be the equation to be solved)

**How is the operation calculated?**

**The following elements are multiplied:**

**Step 1.**

MULTIPLY 100 * 7 = 700

**Step 2.**

DIVIDE 700 / 30 = 23.3333

**23.3333% IS THE PERCENTAGE OF RED COLOURS**

**Another example is the following:**

The number you are looking for the percentage of, multiply it by the percentage you are interested in and divide it by 100.

**3% of $100 is $3.00, so 3% x 100 = 300.**

**Example How much is 25% of 40?**

**The number I am going to look for the % is 40 and the percentage I am interested in is 25%.**

**Step 1**

**40 X 25 = 1000**

**Step 2**

**then the amount of the result you divide by 100**

**1000 รท 100 = 10**

**One more example What is 30% of 80?**

80 X 30 = 24002400

รท 100 = 24

*A More Practical Approach*

When you do not have a calculator or a computer at hand, it is possible to calculate it mentally.

*Case 1*

**We have a storewide 25% discount and you want to buy a screen that costs 4249 pesos.**

*Solution:*

In this case, to make a very quick calculation, the first thing to do is to round the figure.

**Ideally, leave it at 4200 or 4300, so it will be easier to calculate.**

**I will choose 4,300 because I prefer to have money left over from the calculation I will make.**

Then he removed the two zeros that exist in the figure to simplify a bit more, but I have to remember how many there were to know how many to add at the end.

*4,300 ==> 43*

Simplifying is the key, so in order to keep it simple I will also simplify my percentage into 2 parts: 2 and 0.5

**43*2 = 86**

**43 * 0.5 = 21.5 or the same:**

**Half of 43 is 21.5**

*now add: 86+21.5= 87.5*

*Let's remember that we removed 2 zeros from 4,300, now we only have to add them, removing one, which in this case is more a matter of moving the decimal point to the right: 875.*

**How to calculate a percentage with a calculator**

**lesson**

To get a percentage with a calculator, first use the calculator to divide the number by 100. Then, open the calculator screen and divide the number by 100 to get the percentage.

Need another example?

100% of 25 equals 25. So you could say that I have a 25% chance of being sick if I have been sick at least one day this month. That's good!

You can already make a percentage of 100!

**Do you have a calculator?**

So let's make this easier!

I will give you a simpler example, a classic one:

There is a Night Sale, yes, those that everyone likes and you want to buy a LED screen that has a price of $11,499. The whole shop has a 20% discount and you want to know what the final price will be.

Personally I sometimes forget to remember which number goes between which, but for this type of calculation we will omit the division, so there are 2 options:

**Option 1:**

**Multiply on your calculator 11,499 * 0.2 **

**The result is: 2,299.8.**

**That will be your Screen discount.**

**If I want to know how much I will pay in the end I must subtract**

**11,499 - 2299.8 = 9,199.20**

**Option 2:**

As I find it more complicated to take the discount and then subtract it from the final amount, I prefer to do my calculations the other way round. That is, instead of multiplying by 20%, I multiply by 80%, which is what I will pay in the end. To know what you will pay at the end you have to subtract the percentage of your discount from 100, in this case it is 20, so 100 - 20 = 80.

**Multiply 11,499 * 0.8**

**The result is 9,199.20**

**That's what I'll pay for the Screen in the end ๐**

**Practical Examples of Percentages**

In the following examples, what percentage does each number represent?

90%

9 out of 10 people

90% = 9 out of 10 people. 90% means nine out of 10 people.

**Then there are other quick ways of calculating the percentages**

A. To calculate 10% of 20: 10% of 20 = 2

B. To calculate 10% of 30: 10% of 30 = 3

A. To calculate 20% of 20: 20% of 20 = 4

B. To calculate 20% of 30: 20% of 30 = 6

**How to Calculate Credit Card Interest**

This is a very important issue, as many of us can find it difficult to interpret our credit card statements.

The first thing to know before accepting or applying for a credit card is the interest rate on your purchases, often referred to as CAT (Total Annual Percentage Rate), which is how much it will cost you to make purchases and pay for them over time.

Credit card interest is calculated annually, but there are some credit cards that also charge late interest (for late payment), so you should be careful in the clauses of your contract.

"This is a very important issue, as it can be difficult for many of us to interpret our credit card statements".

-The first thing to know before accepting or applying for a credit card is the interest rate on your purchases.

Credit card interest is calculated annually, but some credit cards also have monthly interest rates. The most common credit card interest rates are 16% to 25%.

The reason for the high rates is that it is not only about how much you owe for the goods you buy, but also about how much you can pay in a year or a month.

Some credit cards even offer 0% interest on purchases if the balance is paid in full each month.

To avoid paying huge interest rates on your credit card every month, you should make sure you avoid carrying a balance and always pay your credit card in full every month.

**Let's take an example:**

Your credit card has an **annual **interest rate of **40%**.

If you owe **3,000 **but you couldn't pay more than the minimum which depends on different things, but let's say it's **$150 **your balance is $2,850 in principal. Now let's calculate the interest.

The 40% annual interest rate should be divided by the 12 months of the year and that will be your monthly interest. In this case: **3.33%.**

So to calculate your interest we can do the following:

**Multiply $2,850 * 0.033 **which is the best way to simplify the rule of 3 (we save the last step of dividing by 100).

**Your interest will be 94.05**, which may seem low to some, but if you pay something similar every month, then in one year you will have paid around $1000 in interest alone, which is like giving money to the bank.

This is why most lending institutions recommend that you pay more than the minimum.

If the calculations don't add up, I recommend that you carefully review your statement and your credit card contract. It is likely that some late interest or even an additional charge for not paying by the due date has also been added.

**Important Tips For Your Credit Card Use**

- Check what is the Minimum Payment amount for NO INTEREST, it usually appears on your statement of account under the Minimum Payment, if you always pay that amount, you will never pay interest to the Bank ๐
- If you can't pay more than the Minimum Payment, at least pay by the date shown on your statement. Failure to do so may result in additional charges that are even greater than the interest itself.
- It may sound like an absurd idea, but if you don't have the cash to make the minimum payment it's even better to withdraw from the same credit card to pay it off, it's like refinancing your debt, but you'll avoid the penalty for not paying and a bad credit history.
- Try to buy only at Months Without Interests, some e-commerces give you this option.
- Always calculate the amount of monthly payment you currently make to your bank, even if you buy on interest-free months, if your instalment is too high, then your ability to pay will be affected.
- A basic proposal is that credit card payments should not exceed 20% of your salary, if you do not have other high payments such as a mortgage, otherwise, try to have more balanced finances.
- For example, if you have a salary of 10,000 coins per month (let's not give a currency type to make the example easier) and you pay 2,000 coins on your mortgage, your basic expenses for food, transport and utilities do not exceed another 2,000 coins, then you can afford to pay another 2,000 coins on your credit card. This would give you a liquidity of 40% of your salary for entertainment, unforeseen expenses such as health emergencies and savings.
- if your basic and mortgage expenses exceed 50% of your salary, then try not to commit your credit card to payments that can exceed 10% of your salary, even if they are interest-free payments. This will allow you to have healthier finances.

**Whenever you see a 50% settlement apply these calculations.**

The calculation is:

1.- The original price multiplied by 0.5 (50%) and this result is the final price with the discount.

2.- If the original price is $90 we multiply by 0.5 (50%) i.e. 45 is the final price with discount.

3.- If the original price is $150 we multiply by 0.5 (50%) i.e. 75 is the final discounted price.

4.- If the original price is $180 we multiply by 0.5 (50%) i.e. 90 is the final discounted price.

5.- If the original price is $250 we multiply by 0.5 (50%) or 125 would be our new discounted price.

6.- You can also do the same operation but instead of dividing by 0.5 we divide by 1/2. This is called half the original value and would give us the same result as dividing by 0.5.

7 - Also check if the original price is divided by $100, because if it is, there is no need to do any calculation as half of the original value is exactly the same price as the original with a 50% discount.

8.- If the discount were 25%, the operations are the same but instead of multiplying by 0.5 we multiply it by 0.75 (75%) and this would give us the final price with discount.

9.- If the discount were 50%, the operations are the same but instead of multiplying by 0.5 we multiply it by 1 or 100% and this would give us the final price with discount.

10.- Instead of dividing by 0.5 (50%) or 1/2 as we say, you can also divide by 2 (100%) and if so, at the end you will have half the original value.

11.- If you get a settlement of 75% you can apply the last two examples, although in this case it would be 50% for settlements of less than 75%.

12.- In some settlements the percentage of the discount is used instead of half the original value.

13.- If you don't know what a discount or liquidation is, you can read this article where I explain what a discount is in the administration and liquidation of purchases.

14.- And if the discount is more than 50% you can apply the last two examples and therefore for a discount of 80% you could say that the final price would be half of the original value with a discount of 100%.

15.- You may also be interested in this article on how to calculate travel expenses.

16.- And if you want to know how to calculate VAT you can read this article where I explain 11 basic aspects of VAT for companies and freelancers.

**Examples requested on Facebook:**

These are several questions that were asked in the comments box, recently Facebook modified the plugin and they were deleted. Fortunately they could be rescued to see if any of them could be among your doubts.

**1. Question: 45 is that percent of 30?**

**Response: **

**You divide 100/30 and multiply it by 45****100/30= 3.333 x 45 = 149.9% almost 150%.**

**2. Question: Hello can you help me with this. The number 25 corresponds to 50% of a number. What percentage of that same number does the number 30 correspond to?**

**Response:**

**Multiply 25 *2 = 50, since you want to get 100%.****100/50= 2 x 30= 60%**

**3.Question: I want to know how much is 30% of 240.000**

**Response:**

**Multiply 240 x 0.3 = 72 is 30% of 240.**

**4.Question: How much is an item for sale that costs 800 pesos and has a 30 percent discount?**

**Response:**

**You multiply 800 * 0.3 = 240 - nowthat you have what 30% of 800 equals, you justsubtract: 800 - 240 = 560.**

**5.Question: How much is an item for sale that costs 800 pesos and has a 30 percent discount?**

**Response:**

**You multiply 800 * 0.3 = 240 - nowthat you have what 30% of 800 equals, you justsubtract: 800 - 240 = 560.**

**Question: How do you solve this problem? Which number increased by 14โ
results in 45.6**

**Response:**

**You divide 45.6 / 114, because in this case you don't want to get 100%, but 114%.****45.6/114= 0.4 now you multiply it by 100, to know what would be 100%.****0.4 * 100= 40 is the number that increased by 14% gives as a result 45.6**

**7.Question: what is 18% of 7000?**

**Response:**

**The simplest way to perform such a calculation is to multiply the amount you want the percentage of, in this case 7,000 by the amount you want to know the percentage of, but divided by 100, in this case 18/100 = .18.****7,000 x .18 = 1260****18% of 7200 = 1260.**

**Question: How do you solve this problem? Which number increased by 14โ
yields 45.6**

**Response:**

**You divide 45.6 / 114, because in this case you don't want to get 100%, but 114%.****45.6/114= 0.4 now you multiply it by 100, to know what would be 100%.****0.4 * 100= 40 is the number that increased by 14% gives as a result 45.6**

**Question: If I get paid 25,000 and I get paid 28,000, what percentage increase was it?**

**Response:**

**First let's take out the difference that you were increased, by subtracting the original charge from the new one.****28,000 - 25,000 = 3,000**

**Now we apply the rule****25,000 is our 100%.**

**We want to know to what percentage 3,000 of the total 25,000 corresponds to****3000 x 100 = 300,000****300,000 / 25,000 = 12**

**12% was the percentage increase.****You can check this by multiplying 25,000 x 1.12 = 28,000.**

**10.Question:Hi , question , if a bank gives 18.79% for 30 days fixed term , how would the account be for depositing $150000 , thanks**

**Response:**

**The simple and exact way is to multiply 150,000 x 0.1879 = 28,185.**

**If you want a rough, mental calculation, raise that percentage to 20%, remove zeros for simplicity: 15 x 2 = 30, now return the number of zeros you removed minus one.**

**In this case you took off 4, only 3 comes back. That would leave 30,000 which you will notice when you check it is very close to the 28,185 that comes out in the exact calculation.**

**11.Question:I am going to sell something and I want 4.000.000.000 but the site charges me 11% of the total price for sale that is to say I can not only add 440.000 that is 11% of 4.000.000.000 because that 440.000 also have 11% what will be the exact amount for me to be 4.000.000.000 taking off the 11% of the page mercadolibre**

**Response:**

In this case what you want to calculate is the selling price where the rules change, the formula is as follows:

Selling Price = Cost / (1 - % discount)

In your case it would look like this:

4,000,000 / (1 - 0.11) = 4,000,000 / .89 = 4,494,382.02

*Viral Twitter trick on how to calculate percentages quickly*

On Twitter a publicist by the name of ** Ben Stephens **and his post has gone viral for the way he quickly calculates an amount in percentages.

"** If you need to know what 4% of 75 is without a calculator, just change the order and put it backwards, 75% of 4, which is a bit easier and simpler for everyone**."

In this case, 75% of 4 is 3, and 3 is also 4% of 75.

The tip is with the following formula: ** "X% of y = y% of X"**. In both cases the answer is 3.

Similarly, trying to calculate 18% of 50 can be a headache, but by applying the twitter viral formula, we know that 18% of 50 equals 50% of 18.

And ** 50% of 18 is 9**, which is easier to calculate, right?

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