Step 1:
The first step to converting 12643.421835939 to a fraction is to re-write 12643.421835939 in the form p/q where p and q are both positive integers. To start with, 12643.421835939 can be written as simply 12643.421835939/1 to technically be written as a fraction.
Step 2:
Next, we will count the number of fractional digits after the decimal point in 12643.421835939, which in this case is 9. For however many digits after the decimal point there are, we will multiply the numerator and denominator of 12643.421835939/1 each by 10 to the power of that many digits. So, in this case, we will multiply the numerator and denominator of 12643.421835939/1 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 12643.421835939 as a fraction:
88504/7 / 1