500 Times 0 15
500 × 0.15 = 75. Multiplying by 0.15 is the same as taking 15% of a number, so 75 is also 15% of 500.
500 × 0.15 = 75. Multiplying by 0.15 is the same as taking 15% of a number, so 75 is also 15% of 500.
That one line answers the question. The rest of this page explains why the two are the same, gives you a quick way to check the answer without a calculator, and covers the decimal-place slip that turns 75 into 750.
Why multiplying by 0.15 means "15 percent"
"Percent" means "per hundred." Fifteen percent is 15 out of every 100, which you can write as a fraction or a decimal:
15% = 15/100 = 0.15
So when you multiply 500 by 0.15, you are really multiplying 500 by 15/100:
500 × 15 ÷ 100 = 7,500 ÷ 100 = 75
Whether you think of the problem as a decimal multiplication or as "15% of 500," you are doing exactly the same arithmetic. That is why a sales tax rate of 15%, a 0.15 commission factor and "fifteen hundredths" all lead to the same number.
Check it in your head: 10% plus 5%
Fifteen percent splits neatly into two easy pieces:
- 10% of 500 is 50. Move the decimal point one place left.
- 5% of 500 is 25. It is half of 10%.
Add them: 50 + 25 = 75. This is the same trick people use to work out a 15% tip, and it is a fast way to confirm that a calculator result is in the right range.
The decimal-place slip to watch for
The most common mistake is moving the decimal point the wrong number of places. Each of these looks similar but gives a very different answer:
| Calculation | Percentage it represents | Result |
|---|---|---|
| 500 × 0.015 | 1.5% | 7.5 |
| 500 × 0.15 | 15% | 75 |
| 500 × 1.5 | 150% | 750 |
A quick sense check catches the error. Fifteen percent is a small slice, less than a fifth, so the answer has to be well under 100 when you start from 500. If you get 750, the multiplier was 1.5, not 0.15.
15% of 500 vs. 500 plus 15%
Pay attention to what the question is really asking. "15% of 500" is the part: 75. But many everyday problems want the total after that part is added or removed:
- 500 increased by 15% is 500 × 1.15 = 575. A price with 15% tax added, for example.
- 500 decreased by 15% is 500 × 0.85 = 425. A price after a 15% discount.
Multiplying by 1.15 adds the 15% in one step, because 1.15 is the original 100% plus 15%. Multiplying by 0.85 keeps the 85% that remains after a 15% cut.
Turning any decimal into a percentage, and back
The same rule works for any number:
- Decimal to percent: multiply by 100. 0.15 becomes 15%, 0.075 becomes 7.5%, 1.2 becomes 120%.
- Percent to decimal: divide by 100. 15% becomes 0.15, 7.5% becomes 0.075, 120% becomes 1.2.
Once a percentage is in decimal form, "X% of Y" is simply decimal × Y. For a fuller walk-through of percentage formulas, including percentage change, see our guide to calculating percentages.
Doing it with the Percentage Calculator
The CalcTower Percentage Calculator handles this directly. Choose the "What is X% of Y?" mode, enter 15 as the percentage and 500 as the number, and it returns 75 along with the steps it used.
The same tool covers the related questions above. Its "increase by" and "decrease by" modes give the 575 and 425 totals, and the "is what percent" mode answers the reverse question, such as "75 is what percent of 500?"
Quick answers
What is 0.15 as a percentage?
15%. Multiply the decimal by 100.
Is 500 × 0.15 the same as 500 × 15%?
Yes. 15% means 15/100, which is 0.15, so both give 75.
What is 500 × 0.15 × 2?
150. Thirty percent of 500, since doubling 15% gives 30%.