Step 1:
The first step to converting 16421.690439902 to a fraction is to re-write 16421.690439902 in the form p/q where p and q are both positive integers. To start with, 16421.690439902 can be written as simply 16421.690439902/1 to technically be written as a fraction.
Step 2:
Next, we will count the number of fractional digits after the decimal point in 16421.690439902, which in this case is 9. For however many digits after the decimal point there are, we will multiply the numerator and denominator of 16421.690439902/1 each by 10 to the power of that many digits. So, in this case, we will multiply the numerator and denominator of 16421.690439902/1 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 16421.690439902 as a fraction:
213482/13 / 1