You have come to the right place if you want to know if 0.51 is a rational number. We will explain, and show you with math, why 0.51 is a rational number, or why it is not a rational number.
A rational number is a number that can be expressed as a fraction where the numerator is a whole number (integer) and the denominator is a whole number (integer).
0.51 is the same as 0.51 over 1. In other words, 0.51 can be written with a numerator and denominator, like this:
You can multiply the numerator and denominator of any fraction by the same number and keep the value of the fraction the same. Here we will multiply the numerator and denominator by 100 to get rid of the decimal point.
When we calculate the numerator and the denominator above, we get this fraction:
The fraction above is the same as 0.51. Furthermore, the numerator and the denominator of the fraction above are integers. Therefore, we can conclude that the answer to "Is 0.51 a rational number?" is yes.
Here you can check if another number is rational.