Step 1:
The first step to converting 640637.9455947 to a fraction is to re-write 640637.9455947 in the form p/q where p and q are both positive integers. To start with, 640637.9455947 can be written as simply 640637.9455947/1 to technically be written as a fraction.
Step 2:
Next, we will count the number of fractional digits after the decimal point in 640637.9455947, which in this case is 7. For however many digits after the decimal point there are, we will multiply the numerator and denominator of 640637.9455947/1 each by 10 to the power of that many digits. So, in this case, we will multiply the numerator and denominator of 640637.9455947/1 each by 10000000:
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 640637.9455947 as a fraction:
640638/1 / 1