There's a bit of a silly trick to multiplying decimals. It's not really a trick -- it's just how it works -- but, it's so weird that it may seem like a trick.
It's going to sound confusing at first. Just read through it, then look at the examples, then read it again. It'll be really easy!
Here's the deal:
|1)||Ignore the decimal points and multiply as usual...|
|2)||Count how many total digits are on the right side of the decimal points in the guys you are multiplying...|
|3)||Place the decimal point in your answer so there are this many digits to the right.|
Let's just do one!
Multiply... Count the spots behind the decimals... Put the decimal point in your answer:
Does our answer make sense? Do a little rounding and think about it... 2.8 is a little less than 3... 3 x 7 = 21... So, our answer should be a little less than 21. Yep, our answer looks good!
And remember, you can always grab a calculator to check your answers on these!