Calculating ratios is a basic mathematical skill that has many practical applications in everyday life. From calculating discounts and benefits to understanding statistics and data, percentage calculations allow us to show changes and compare values in a simple and understandable way.

The percentage is often displayed with a % sign, but it is recommended that you type the percentage in Norwegian. If you are going to write a number with a sign, then it is recommended to write it with a space between the number and the sign, i.e. like this: 10%.

There are two ways we talk about calculating percentages. One relates to the amount of a part of something, the percentage. The second is to show the percentage change increase or decrease.

- For example, 20 is the answer to 10 percent of 200.
- The 10 percent increase from 200 is also 20 in numbers, but in percentage terms the change is 10.

## How do you calculate the percentage?

Percentage means per hundred. 1 in 100 is 1 percent. If you’re going to calculate a percentage, 100 something must always be included in the calculation one way or another.

For example, if you wanted to calculate how much of a discount you would get on a price if you had a 30 percent discount, you would calculate like this:

The price you should calculate based on multiplying by 30 (percentage)

Then you divide this by 100

A quick trick for many is instead of multiplying by 0.3 – especially if you have a calculator in front of you, it goes faster that way. This is because Percentage / 100 gives you the choice of no matter what type of percentage you will calculate from. If it’s 10 percent, multiply by 0.1, and if it’s half price (50 percent), then multiply by 0.5. Then you will know what rejection is.

So if the dress costs 1,000 NOK and you have a 30 percent discount, you multiply 1,000 by 0.3, which gives you 300 NOK. So you get 300 NOK for the dress.

If you want to know the percentage of something, the calculation is slightly turned upside down. Then you have, say, 300, and you want to know what kind of percentage the 1000 is. Then the calculation goes like this:

300/1000 (the part of the number divided by the whole number). This time I saw with 100. That becomes 30 percent.

If you want to calculate changes in percentage, you have to know the real change. For example, if the value of the house increased from 700,000 to 1,000,000, the change would be 300,000. The whole number you have to calculate from is the value. That’s 700,000 and that means you have to calculate 300,000 multiplied by 100 divided by 700,000. Which means the change is 42.86 percent (rounded). Since it’s 300,000, it might be tempting to say 30 percent because 300,000 is 30 percent of 100,000, but the percentage change is calculated based on the value.

What if you have the percentage and not the whole number? Let’s say 5 percent of Skedsmo Handball Club players suffer from knee injuries. You know there are 3 people. Then you multiply 3 by 100 and divide by 5. This means that there are 60 people playing handball. So the procedure is to take the number you have, multiply it by 100 and then divide by the percentage.

## What is the percentage?

One of the most common errors in references to percentages is, for example, writing that the Center Party has increased support by 2 percent if the increase is from 8 percent of those who answered 10 percent. This may sound correct, but a two percentage point increase is a valid description. In percentage terms, the increase was 25. This is because 2 is 25 percent of the original 8.

## What is the blood alcohol level?

Promelle means one in a thousand. For example, the percentage of alcohol in the blood is not given as a percentage, but in thousandths. Each mile has a tenth of a percent and is represented by a ‰ sign.

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