Find the absolute value

So what my teacher taught me with decimals is say you have a problem and it’s 3.27 x 1.6 you would take you first problem which is 3.27 and look how many numbers are behind the decimal 2 and then you go to your next problem you have 1.6 how many numbers are behind that 1 so you would add them both up and you have three and you start from the back once you get your answer and count however many