2.1 x 3.2 = 6.72
21 x 32 = 672
As you can see, both products contain the same set of numbers however these numbers have different values.
6.72 = 6 is in units place, 7 is in tenths place, 2 is in hundredths place
672 = 6 is in hundreds place, 7 is in tens place, 2 is in units place
The main reason of their differences is the presence of decimal points. In multiplying numbers with decimals, the count of the numbers after the decimal point in the product can be determined by the count of the numbers after the decimal point in the factors.
2.1 has one number after the decimal, 3.2 also has 1 number after the decimal. a total of 2 numbers after the decimal, which reflects to its product 6.72