What is 20 Percent of 42?
20% of 42 = 8.4
Step by step
- Turn the percentage into a decimal: 20 ÷ 100 = 0.2
- Multiply: 0.2 × 42 = 8.4
How the answer is worked out
“Percent” means “per hundred”, so 20% is 20 out of every 100, or 0.2 as a decimal. Taking 20% of 42 means multiplying 42 by 0.2, which gives 8.4.
8.4 is the 20% share of 42. The remaining 80% is 33.6, and the two parts add back up to 42.
Why calculate this?
Taking a percentage of a number is how discounts, tips, tax and interest are worked out.
- Discounts: 20% off an item priced $42 saves $8.4, so you pay $33.6.
- Tips: a 20% tip on a bill of $42 is $8.4, so the total is $50.4.
- Interest: simple interest of 20% a year on $42 earns $8.4 in one year and $42 over five years.
- Tax: a sales tax of 20% on a price of $42 adds $8.4, so the price including tax is $50.4.
A quicker way
Use 10% and 1%: 10% of 42 is 4.2 and 1% is 0.42. 20% is 2 × 10% = 8.4 = 8.4.
Swap the numbers if that is easier: 20% of 42 is always the same as 42% of 20, because both are 20 × 42 ÷ 100.
Check the answer
Work backwards: 8.4 ÷ 42 × 100 = 20%. Getting 20% back shows the answer is right.
Rounding
Rounded to a whole number the result is 8, to one decimal place 8.4 and to two decimal places 8.40. Round only at the end: rounding halfway through a calculation can change the last digit.
The formula explained
result = percentage ÷ 100 × number. Dividing the percentage by 100 turns it into a decimal multiplier, so 25% becomes 0.25 and 150% becomes 1.5. Multiplying the number by that decimal gives the share.
Another worked example: 4% of 31
- Turn the percentage into a decimal: 4 ÷ 100 = 0.04
- Multiply: 0.04 × 31 = 1.24
Common percentages of 42
10% of 42 is 4.2, 20% is 8.4, a quarter (25%) is 10.5, half (50%) is 21 and three quarters (75%) is 31.5. Knowing these makes it easy to estimate any other percentage of 42 in your head.
Adding and taking away 20%
Increasing 42 by 20% gives 50.4 and decreasing it by 20% gives 33.6. These do not cancel out: raising 42 by 20% and then lowering the result by 20% ends at 40.32, because the second 20% is taken of a bigger number.
Finding the original number
If 8.4 is 20% of something, divide by 0.2 to get it back: 8.4 ÷ 0.2 = 42. This is how you work out a price before tax or a full amount from a share of it.
Other ways to ask this
The same calculation is often asked in other words. All of these have the answer above:
- What is 20 percent of 42?
- 20% of 42
- 20 percent times 42
- Find 20% of 42
- How much is 20 per cent of 42?
Terms used on this page
- Percentage: the rate, the number with the % sign.
- Base: the number you take the percentage of.
- Decimal multiplier: the percentage divided by 100.
- Mark-up and discount: adding or taking away a percentage of a price.
The answer in other forms
| Result | 8.4 |
|---|---|
| Remaining | 33.6 |
| 20% as decimal | 0.2 |
| 42 + 20% | 50.4 |
Related results
| 5% of 42 | 5% of 42 = 2.1 |
| 10% of 42 | 10% of 42 = 4.2 |
| 15% of 42 | 15% of 42 = 6.3 |
| 25% of 42 | 25% of 42 = 10.5 |
| 50% of 42 | 50% of 42 = 21 |
| 75% of 42 | 75% of 42 = 31.5 |
The other way round: 42% of 20
Doing it in a spreadsheet
In Excel, Google Sheets or Numbers type =20%*42 into any cell. Replace the numbers with cell references (for example A1 and B1) to reuse the formula for a whole column.
Common mistakes
Forgetting to divide the percentage by 100 makes the answer 100 times too big. Note that x% of y always equals y% of x.
Practice examples
| 4% of 31 | Show answer4% of 31 = 1.24 |
| 44% of 25 | Show answer44% of 25 = 11 |
| 78% of 90 | Show answer78% of 90 = 70.2 |
| 52% of 64 | Show answer52% of 64 = 33.28 |
| 47% of 43 | Show answer47% of 43 = 20.21 |
| 84% of 47 | Show answer84% of 47 = 39.48 |
| 51% of 43 | Show answer51% of 43 = 21.93 |
| 8% of 15 | Show answer8% of 15 = 1.2 |
| 44% of 43 | Show answer44% of 43 = 18.92 |
| 24% of 12 | Show answer24% of 12 = 2.88 |
How this answer was calculated
The result is worked out from the numbers in this page's address when the page is opened, using exact arithmetic wherever possible and rounding only for display. Nothing is copied from a printed table. If you think an answer is wrong, please tell us through the contact page and we will check it.
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Questions
What is 20 Percent of 42?
20% of 42 is 8.4. Formula, steps and practice examples.
What is 20% off 42?
33.6. Taking 20% off leaves 80% of 42.
What is 42 plus 20%?
50.4. Adding 20% is the same as multiplying by 1.2.
What is 20% of 42 as a fraction?
20/100 × 42 = 840/100, which simplifies to 42/5.
How do I find 20% of a number on a calculator?
Multiply the number by 0.2. For 42 that is 42 × 0.2 = 8.4. On many calculators you can also type 42 × 20 %.