Multiplying Decimals Animations
How to Multiply Decimals
Multiplying decimals starts with normal multiplication (ignoring decimal points).
Then the trick is to make sure the answer has as many decimal places as the two original numbers combined.
See the animation (press the play button):
We had to put the decimal point 3 places along.
Note how I put the longer number on top (the one with the most digits) ... this made it easier to do the multiplication.
Here is another example, using long multiplication:
We had to put the decimal point 5 places along, but there were only 4 digits, so that meant we had to insert another zero.
Zeros at the end
What if there are zeros at the end? Keep them there while you work out where to put the decimal point.
BUT when we we write down the final answer we can leave off any zeros at the end (unless we are asked to keep them there), like this:
In that example the decimal points were put in after the multiplication, it doesn't matter which way we do it so long as we remember to count the correct number of places.