Is 8.1 equal to 81 percent?

Answer 1

No. First, when you discuss a percentage, you are really discussing a ratio of two numbers, so you can't really speak about "8.1" being a percent. But 8.1 is some percent of something. For example,

8.1 is 8.1% of 100

8.1 is 81% of 10

8.1 is 10% of 81, etc.

Percents are just a way of describing a ratio, and it is equal to the ratio multiplied by 100. More examples:

The ratio 2/5 can also be written as 0.4. Multiply this by 100 to get 40, and adds the percent sign, 40%. So you say that 2 is 40% of 5.

The ratio 3/9 is about 0.333 and can also be written as 33.3%.

Now, often with fractions between 0 and 1, such as 0.75, people take for granted that this is an expression of a ratio, for example, 0.75 is the same as 3/4 and 75%. The denominator of the ratio in this case is assumed to be 1. People don't usually take that assumption in cases where the ratio is >1, but if you did, in your example, 8.1 / 1 would be 810%.