How to calculate percentages
We write the percentage as a decimal and multiply: 15% of 240 is 0.15 · 240 = 36. To find what percentage a is of b, we work out a ÷ b: 18 ÷ 72 = 0.25 = 25%.
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Percentage calculator
- 1 % av 240 är 240 ÷ 100 = 2,4
- 15 % är 15 gånger så mycket: 15 · 2,4 = 36
- Med decimalform: 15 % = 0,15, och 0,15 · 240 = 36
- Svar: 15 % av 240 är 36
What does percent mean?
Percent means hundredths. 15% is 15 out of 100 equal parts. The whole, the amount we compare with, is always 100%.
15% = .15
| Percent | Hundredths | Decimal | Means |
|---|---|---|---|
| 1% | 1/100 | 0.01 | one hundredth |
| 10% | 10/100 | 0.1 | one tenth |
| 25% | 25/100 | 0.25 | one quarter |
| 50% | 50/100 | 0.5 | half |
| 100% | 100/100 | 1 | the whole |
The part, the whole and the percentage
If we know two of the three, we can work out the third. Ask first: what is the whole? It is the amount we compare with.
- The part = the percentage · the whole: 0.15 · 240 = 36.
- The percentage = the part ÷ the whole: 18 ÷ 72 = 0.25 = 25%.
- The whole = the part ÷ the percentage: 30 ÷ 0.20 = 150.
The 1% method and decimal form
We want to know how much 15% of 240 is.
First we work out 1%, one hundredth, and then take 15 of them.
1% of 240 = 240 ÷ 100 = 2.4
15% of 240 = 15 · 2.4 = 36
In decimal form it takes one step. Divide the percentage by 100: 15% = 0.15, 8% = 0.08.
0.15 · 240 = 36
Example
Example 1: How much is 15% of 240 kr?
The whole is 240 kr. We want to know how much 15 hundredths of it is.
First we work out 1%, one hundredth of the whole.
240 ÷ 100 = 2.4
We want 15 of those parts.
15 · 2.4 = 36
In decimal form, 15% = 0.15.
0.15 · 240 = 36
15% of 240 kr is 36 kr.
36 ÷ 240 = 0.15 = 15%. That is correct. It is reasonable too: 10% is 24, so 15% should be a little more.
Example 2: What percentage of the class cycles?
12 out of 32 pupils cycle to school. We want to know what percentage that is. The whole is 32.
We divide the part by the whole.
12 ÷ 32 = 0.375
We multiply by 100 to get hundredths.
0.375 · 100 = 37.5
The share is 37.5 hundredths.
0.375 = 37.5%
Backwards: 0.375 · 32 = 12. That is correct. It is reasonable: 12 is a little under half of 32, and 37.5% is a little under 50%.
Example 3: Decrease 640 kr by 25%
A jacket costing 640 kr is reduced by 25%. We want to know the new price.
The reduction is 25% of 640 kr.
0.25 · 640 = 160
We subtract the reduction from the old price.
640 − 160 = 480
Or directly: what is left is 100% − 25% = 75% of the price.
0.75 · 640 = 480
The new price is 480 kr.
480 ÷ 640 = 0.75, so 75% of the old price. That is correct.
Pitfalls
Dividing by the percentage, so that 15% of 240 becomes 240 ÷ 15 = 16.
Percent means hundredths. Divide by 100 to get 1%, or multiply by the decimal: 0.15 · 240 = 36.
Dividing the wrong way round, so that 12 out of 32 becomes 32 ÷ 12 ≈ 2.67.
The part comes first and the whole last: the part ÷ the whole, 12 ÷ 32 = 0.375.
Writing 5% as 0.5.
Divide by 100: 5 ÷ 100 = 0.05. 0.5 is 50%, which is half.
Practise on your own
0 of 4 correct1How much is 10% of 350 kr?
2A summer worker gets a bonus of 450 kr and saves 6% of it. How many kronor do they save?
3A bus has 60 seats and 27 of them are taken. What percentage of the seats are taken?
4A pair of shoes costs 800 kr and is sold at a 35% discount. What is the new price?
More walkthroughs with Fox
Common questions
How do you calculate percentages on a calculator?
Write the percentage as a decimal and multiply: 0.15 · 240 = 36. To find what percentage 18 is of 72: 18 ÷ 72 = 0.25, so 25%.
How do you find the whole when you know the percentage and the part?
Divide the part by the percentage in decimal form. If 30 kr is 20% of the amount, the whole is 30 ÷ 0.20 = 150 kr.
Can something be more than 100%?
Yes, when the part is bigger than the whole. 150% of 80 is 1.5 · 80 = 120.
What is the difference between percent and percentage points?
Percentage points are the difference between two percentages. From 2% to 3% is an increase of 1 percentage point, but of 50 percent.
Read also
- Years 7–9Percentage change: increase and decreaseHow do you work out a percentage increase or decrease?
- Years 5–9Fractions, decimals and percentagesHow do you convert fractions to decimals and percentages?
- Years 7–9 and upper secondaryDiscount and VATHow do you work out a discount and VAT?
- Years 8–9 and upper secondaryChange factor (percentage multiplier)What is a change factor and how do you use it?
- Years 8–9 and upper secondaryPercent and percentage pointsWhat is the difference between percent and percentage points?
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