Step 1:
The first step to converting 6436.3721987091 to a fraction is to re-write 6436.3721987091 in the form p/q where p and q are both positive integers. To start with, 6436.3721987091 can be written as simply 6436.3721987091/1 to technically be written as a fraction.
Step 2:
Next, we will count the number of fractional digits after the decimal point in 6436.3721987091, which in this case is 10. For however many digits after the decimal point there are, we will multiply the numerator and denominator of 6436.3721987091/1 each by 10 to the power of that many digits. So, in this case, we will multiply the numerator and denominator of 6436.3721987091/1 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 6436.3721987091 as a fraction:
51491/8 / 1