Step 1:
The first step to converting 339.78854831368 to a fraction is to re-write 339.78854831368 in the form p/q where p and q are both positive integers. To start with, 339.78854831368 can be written as simply 339.78854831368/1 to technically be written as a fraction.
Step 2:
Next, we will count the number of fractional digits after the decimal point in 339.78854831368, which in this case is 11. For however many digits after the decimal point there are, we will multiply the numerator and denominator of 339.78854831368/1 each by 10 to the power of that many digits. So, in this case, we will multiply the numerator and denominator of 339.78854831368/1 each by 100000000000:
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 339.78854831368 as a fraction:
17669/52 / 1