Step 1:
The first step to converting 398939.779875 to a fraction is to re-write 398939.779875 in the form p/q where p and q are both positive integers. To start with, 398939.779875 can be written as simply 398939.779875/1 to technically be written as a fraction.
Step 2:
Next, we will count the number of fractional digits after the decimal point in 398939.779875, which in this case is 6. For however many digits after the decimal point there are, we will multiply the numerator and denominator of 398939.779875/1 each by 10 to the power of that many digits. So, in this case, we will multiply the numerator and denominator of 398939.779875/1 each by 1000000:
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 398939.779875 as a fraction:
398940/1 / 1