Step 1:
The first step to converting 257.0390980416 to a fraction is to re-write 257.0390980416 in the form p/q where p and q are both positive integers. To start with, 257.0390980416 can be written as simply 257.0390980416/1 to technically be written as a fraction.
Step 2:
Next, we will count the number of fractional digits after the decimal point in 257.0390980416, which in this case is 10. For however many digits after the decimal point there are, we will multiply the numerator and denominator of 257.0390980416/1 each by 10 to the power of that many digits. So, in this case, we will multiply the numerator and denominator of 257.0390980416/1 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 257.0390980416 as a fraction:
13109/51 / 1