Step 1:
The first step to converting 664890.75720415 to a fraction is to re-write 664890.75720415 in the form p/q where p and q are both positive integers. To start with, 664890.75720415 can be written as simply 664890.75720415/1 to technically be written as a fraction.
Step 2:
Next, we will count the number of fractional digits after the decimal point in 664890.75720415, which in this case is 8. For however many digits after the decimal point there are, we will multiply the numerator and denominator of 664890.75720415/1 each by 10 to the power of that many digits. So, in this case, we will multiply the numerator and denominator of 664890.75720415/1 each by 100000000:
Step 3:
Now the last step is to simplify the fraction (if possible) by finding similar factors and cancelling them out, which leads to the following answer for 664890.75720415 as a fraction:
664891/1 / 1