When multiplying decimals, how do you determine where to place the decimal in the answer?

Count the numbers right to the decimal point ,and then count that much of numbers from right to left and apply it.
Example:  2.50
             *  2.50
               
               6.2500     There is 4 numbers right to the decimal point totallyand the answer.  

31% × 96.000.000= 29.760.000