Step 1:
The first step to converting 85721.399999904 to a fraction is to re-write 85721.399999904 in the form p/q where p and q are both positive integers. To start with, 85721.399999904 can be written as simply 85721.399999904/1 to technically be written as a fraction.
Step 2:
Next, we will count the number of fractional digits after the decimal point in 85721.399999904, which in this case is 9. For however many digits after the decimal point there are, we will multiply the numerator and denominator of 85721.399999904/1 each by 10 to the power of that many digits. So, in this case, we will multiply the numerator and denominator of 85721.399999904/1 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 85721.399999904 as a fraction:
257164/3 / 1