Lets say that u r doing the problem. 5.2 x 2.1 there are altogether 2 numbers to the right of the decimal, so you take out the decimals, multiply, and add the decimal 2 numbers to the left.
When you multiply decimals first you should take away the decimals and just leave the number. Then multiply the two numbers together and you get a larger number than the two numbers you have. Then...
Multiply the two numbers together as if there were no decimal places. But if there are any zeros at the end of the multipe don't get rid of them (yet).
Count the number of digits after (to the right...