Step 1:
The first step to converting 121231.78005 to a fraction is to re-write 121231.78005 in the form p/q where p and q are both positive integers. To start with, 121231.78005 can be written as simply 121231.78005/1 to technically be written as a fraction.
Step 2:
Next, we will count the number of fractional digits after the decimal point in 121231.78005, which in this case is 5. For however many digits after the decimal point there are, we will multiply the numerator and denominator of 121231.78005/1 each by 10 to the power of that many digits. So, in this case, we will multiply the numerator and denominator of 121231.78005/1 each by 100000:
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 121231.78005 as a fraction:
484927/4 / 1