-
-
We're asked to multiply 32.12,
or 32 and 12 hundredths, times
-
0.5, or just 5 tenths.
-
Now when you multiply decimals,
you multiply them
-
the exact same way you would
multiply whole numbers, and
-
then you count the number of
spaces behind the decimal you
-
have in your two numbers you're
multiplying, and you're
-
going to have that many spaces
in your product.
-
Let me show you what
I'm talking about.
-
So let's just multiply
these two characters.
-
So we have 32.12 times 0.5.
-
And when you write them out, you
can just push both of them
-
all the way to the right.
-
You could almost ignore
the decimal.
-
Right now, you should write the
decimal where they belong,
-
but you can almost pretend that
this is 3,212 times 5,
-
and then we'll worry about
the decimals in a second.
-
So let's get started.
-
So if we were just multiplying
5 times 3,212, we would say,
-
well, 5 times 2 is 10.
-
Regroup the 1.
-
5 times 1 is 5, plus 1 is 6.
-
5 times 2 is 10.
-
Regroup the 1.
-
And then finally, you have 5
times 3 is 15, plus 1 is 16.
-
And then we don't have
any other places.
-
If we were just doing this as
05, we wouldn't multiply 0
-
times this whole thing.
-
We would just get 0 anyway.
-
So just 5 times 3,212 gives
us this number.
-
But now we want to care
about the decimals.
-
We just have to count the total
number of spaces or
-
places we have behind the
decimal point in the two
-
numbers we're multiplying.
-
So we have one, two, three
spaces, or three numbers, to
-
the right of the decimals in
the two numbers that we're
-
multiplying.
-
So we need that many numbers to
the right of the decimal in
-
our answer.
-
So we go one, two, three, put
the decimal right over there.
-
So 32.12 times 0.5 is 16.060.
-
And this trailing zero right
here we can ignore, because
-
it's really not adding any
information there.
-
So we could just write
this as 16.06.
-
The last thing you want to do
is just make sure that this
-
makes sense.
-
You have a number that's
almost 32, and we're
-
multiplying it by 0.5.
-
Remember, 0.5 is the same thing
as 5 over 10, which is
-
the same thing as 1/2.
-
So we're really multiplying
32.12 times 1/2.
-
We're trying to figure out what
one half of 32.12 is.
-
And half of 32 is 16, and half
of 0.12 0.06, so this makes
-
complete sense.
-
