WEBVTT

00:00:00.000 --> 00:00:00.490


00:00:00.490 --> 00:00:07.030
What is the cost of 14.6 gallons
of gasoline at $2.70

00:00:07.030 --> 00:00:08.290
per gallon?

00:00:08.290 --> 00:00:15.600
So we have 14.6 gallons,
and each gallon's

00:00:15.600 --> 00:00:17.300
going to cost $2.70.

00:00:17.300 --> 00:00:21.530
Or we can even view $2.70
as 2.7 dollars.

00:00:21.530 --> 00:00:25.040
Let's just multiply times 2.7.

00:00:25.040 --> 00:00:26.870
It makes things a little
bit simpler.

00:00:26.870 --> 00:00:30.490
I think you'll appreciate $2.70
is the same thing as 2.7

00:00:30.490 --> 00:00:32.340
dollars per gallon.

00:00:32.340 --> 00:00:35.030
So let's multiply this out.

00:00:35.030 --> 00:00:38.620
So first we have, and just as a
reminder, when you multiply

00:00:38.620 --> 00:00:42.280
decimals, you just have to treat
the numbers like whole

00:00:42.280 --> 00:00:44.760
numbers and then worry about
the decimals later.

00:00:44.760 --> 00:00:49.370
So right now, we can just view
this as 146 times 27, and then

00:00:49.370 --> 00:00:51.060
we'll worry about
the decimals.

00:00:51.060 --> 00:00:53.950
So first we have
a 7 times a 6.

00:00:53.950 --> 00:00:57.040
7 times 6 is 42.

00:00:57.040 --> 00:00:58.530
Regroup the 4.

00:00:58.530 --> 00:01:03.210
7 times 4 is 28, plus 4 is 32.

00:01:03.210 --> 00:01:04.730
Regroup the 3.

00:01:04.730 --> 00:01:08.730
7 times 1 is 7, plus 3 is 10.

00:01:08.730 --> 00:01:13.790
So we get 7 times
146 is 1,022.

00:01:13.790 --> 00:01:15.840
Now we're going to
deal with this 2.

00:01:15.840 --> 00:01:18.380
But this 2, at least before we
consider the decimal, is

00:01:18.380 --> 00:01:19.160
really a 20.

00:01:19.160 --> 00:01:22.310
So we're going to
put a 0 here.

00:01:22.310 --> 00:01:24.600
We're doing it exactly the same
way we do a traditional

00:01:24.600 --> 00:01:25.520
multiplication problem.

00:01:25.520 --> 00:01:27.620
We're ignoring the
decimals for now.

00:01:27.620 --> 00:01:29.430
2 times 6 is 12.

00:01:29.430 --> 00:01:31.660
Carry the 1, or regroup the 1.

00:01:31.660 --> 00:01:33.580
We can ignore these
guys right now.

00:01:33.580 --> 00:01:37.800
2 times 4 is 8, plus 1 is 9.

00:01:37.800 --> 00:01:41.360
2 times 1 is 2, and
now we can add.

00:01:41.360 --> 00:01:44.600


00:01:44.600 --> 00:01:47.410
And we get 2 plus 0 is 2.

00:01:47.410 --> 00:01:49.390
2 plus 2 is 4.

00:01:49.390 --> 00:01:51.720
0 plus 9 is 9.

00:01:51.720 --> 00:01:55.170
1 plus 2 is 3.

00:01:55.170 --> 00:01:58.650
Now we've figured out what
146 times 27 is.

00:01:58.650 --> 00:02:00.950
It's 3,942.

00:02:00.950 --> 00:02:03.070
But this wasn't 146 times 27.

00:02:03.070 --> 00:02:06.030
It was 14.6 times 2.7.

00:02:06.030 --> 00:02:07.980
So now we have to worry
about the decimals.

00:02:07.980 --> 00:02:11.130
We just count how many numbers
are sitting behind decimals.

00:02:11.130 --> 00:02:14.200
We have one right there and
a second one right there.

00:02:14.200 --> 00:02:16.710
So our product has to have
two numbers to the

00:02:16.710 --> 00:02:17.670
right of the decimal.

00:02:17.670 --> 00:02:21.160
So one, two, stick it
right over there.

00:02:21.160 --> 00:02:25.860
So for 14.6 gallons of gas at
$2.70 per gallon, it's going

00:02:25.860 --> 00:02:28.110
to cost $39.42.

00:02:28.110 --> 00:02:31.199