Step 1:
The first step to converting 418.7991 to a fraction is to re-write 418.7991 in the form p/q where p and q are both positive integers. To start with, 418.7991 can be written as simply 418.7991/1 to technically be written as a fraction.
Step 2:
Next, we will count the number of fractional digits after the decimal point in 418.7991, which in this case is 4. For however many digits after the decimal point there are, we will multiply the numerator and denominator of 418.7991/1 each by 10 to the power of that many digits. So, in this case, we will multiply the numerator and denominator of 418.7991/1 each by 10000:
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 418.7991 as a fraction:
91717/219 / 1