Step 1:
The first step to converting 3890.985216999 to a fraction is to re-write 3890.985216999 in the form p/q where p and q are both positive integers. To start with, 3890.985216999 can be written as simply 3890.985216999/1 to technically be written as a fraction.
Step 2:
Next, we will count the number of fractional digits after the decimal point in 3890.985216999, which in this case is 9. For however many digits after the decimal point there are, we will multiply the numerator and denominator of 3890.985216999/1 each by 10 to the power of that many digits. So, in this case, we will multiply the numerator and denominator of 3890.985216999/1 each by 1000000000:
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 3890.985216999 as a fraction:
260696/67 / 1