Step 1:
The first step to converting 408.6570821429 to a fraction is to re-write 408.6570821429 in the form p/q where p and q are both positive integers. To start with, 408.6570821429 can be written as simply 408.6570821429/1 to technically be written as a fraction.
Step 2:
Next, we will count the number of fractional digits after the decimal point in 408.6570821429, which in this case is 10. For however many digits after the decimal point there are, we will multiply the numerator and denominator of 408.6570821429/1 each by 10 to the power of that many digits. So, in this case, we will multiply the numerator and denominator of 408.6570821429/1 each by 10000000000:
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 408.6570821429 as a fraction:
14303/35 / 1