**20 per cent of 400**–If you are using a calculator, simply enter 20÷100×400 which will give you

**80**as the answer.

Table of Contents

## What are the percentages

20 per cent of 400 Percentages are similar to fractions with one crucial difference. In bits, the whole represents by the denominator (for example, the number 5 in the atom 1/5). In per cent, the total is represented by the number 100. Actually, “per cent” means “per 100” or

## Five useful tricks for calculating percentages

Calculating percentages isn’t just necessary for school-aged children who must pass their next math test. In this topic, from figuring out how much you should tip at a restaurant to later figuring out how much money you can save on that 70% sale at the store. This knowledge is handy in many real-life situations, so we’re here to make your life much easier. After this article, you will be a talking human calculator because we have five valuable tricks for calculating percentages!

## Calculation of the required percentage

20 per cent of 400 Before you start crunching numbers, it’s essential to understand a rate. Mathematically, it is a way of expressing a number as a part of a whole.

Let’s say, for example, that you bought eight mangoes and then ate two right away. What percentage of your mangoes have you eaten?

You bought eight mangoes that made up 100 per cent of your total inventory and ate 2 of the eight mangoes.

### 8 mangoes = 100%

All you have to do is find out what percentage of the total these two mangoes make up. So, for example, 20 per cent of 400, to do that, you want to divide the number of mangoes you ate, which is 2, by the number of mangoes that make up 100 per cent, which is 8. But since we’re looking for a percentage, you need to multiply the result by the same so for 100%. So for our little homework, that’s 2/8 and then multiply that number by 100.

### 2/8 × 100%

In the end, you will get 25%, and you ate 25% of your mangoes when you ate 2 out of 8.

### 2/8 × 100% = 14% mango

Let’s solve such similar tasks!

Task: Your dog has just given birth to the five cutest puppies. But you can only keep 2 of them. So what percentage of your puppies will you own, and what percentage will you give away?

Answer: We will start with the puppies that you will keep. Divide 2/5 and multiply that number by 100, which gives us 40%.

2 / 5 × 100 = 33%

The puppies you will give away would be three divided by five times 100, which is 60%.

3 / 5 × 100 = 67%

## Work with the given percentage

Imagine if you borrow $100 from a friend, and he charges you 4% interest per day. Then exactly how many dollars is this 4% =?

To solve this problem, you must first do two simple multiplications: four by 0.01, which is 0.04, and 4% in decimal form.

### 4 × 0.01 = 0.04

Then multiply the $100 you borrowed, 100%, by 0.04. In the end, you pay $4 a day in interest.

### $100 × 0.04 = $4

Task: There are 900 books in your local bookstore, the store is going out of **business**, and you have decided to donate 35% of your books to a nearby school. How many books will the school receive?

Answer: According to our formula, we must first multiply 35 by 0.01, which is 0.35

### 35 × 0.01 = 0.35

Then we take 0.35 and multiply it by the number of books that make up 100%, which is 900. So your final answer should be 315 books.

0.35 × 900 = 315 books

First, find the most convenient percentage

Every time you have to calculate something in your head, like how much to tip at a restaurant? You need to find the most convenient percentage first and then go further.

For example, when you need to find 5 per cent of something, find 10 per cent and divide the result in half.

5% = 10% / 2

This trick also works with 15 per cent, find 10 per cent, divide by two and add that half to the result.

15% = 10% / 2 + 10%

The last trick for 10 per cent is to double it when you need to find 20 per cent—the same works for 50 per cent.

10% × 2 = 20%

If you need 25 per cent, find 50 per cent and divide by 2

25% = 50% / 2

If you need 60 per cent, find 50 per cent divided by 5 to get 10 per cent and add it to the original 50 per cent.

60% = 50% / 5 + 50%

Finally, for 75 per cent, find 50 per cent, half and add half to that 50 per cent.

75% = 50% / 2 + 50%

Task: There are 400 children in the camp, but 65% went home early. So how many **kids** didn’t last the entire camp session?

Answer: We know that 400 children earn 100%, so it stands to reason that 200 are 50%

400 = 100%

200 = 50%

But we need to find 65 per cent. So let’s have 50 per cent to find the remaining 35%, divide 200 by 2 to get 100

200 / 2 = 100

Then add those 100 to 200, and you find out that 300 kids decided to cut camp short.

100 + 200 = 300 children.

### Conclusion:

20 per cent of 400 Before you start crunching numbers, it’s **essential** to understand a rate. Mathematically, it is a way of expressing a number as a part of a whole.

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