In a fraction, we can see how many “pieces” of a number are present (in the numerator) compared to how many pieces would make up the whole (the denominator). “Percent” means “per hundred”, which is like asking the question “how many pieces would there be if there were 100 pieces possible?”
For example, if we look at the percentage 50%, that means we have 50 pieces of the possible 100. Re-writing this in fraction form, we see 50/100.
We can start the process of converting a fraction into a percent, by figuring out how to adjust the fraction so that the denominator will be 100. First, divide 100 by the denominator:
Then we can multiply both the numerator and denominator by this number:
This works because multiplying both the numerator and the denominator by the same number is like multiplying it by 1. (0.123 / 0.123 = 1)
Re-writing the result as a percentage, we can see that 21/812 as a percentage is 2.586%.