simply move the decimal point over the required ammount (laemans terms, the number of zeros in the multiplier.)
1,000,00,00 * 12.456
(if 1,000,00,00 is a typo, and you meant american billion, simply add two zeros to the end of the answer)
answer is 12,456,00,00.
the way that you recieve this answer is all whole numbers, you put the ones in the place of the one, you put the tens in the next decimal point (equal to 10,000,00,00), etc. you simply place the decimals with the zeros corrilating directly to the first zero from the 1 (in 1,000,00,00)
-Rigo