Hello and welcome to Advanced Multiplication.
My name is Kiley, and in this video you'll learn how to multiply numbers between 11 and 20.
Do you remember the multiplication table?
A multiplication table looks like this -
with numbers from left to right, and up and down.
Memorizing the facts of a multiplication table can help you solve basic math problems on the go.
Knowing the multiplication table will help with advanced multiplication too.
If you need a review, watch the video called, "Basic Multiplication."
Multiplication is a short cut for addition.
Multiplying lets you add up multiple numbers very quickly, like this.
Let's practice multiplying a bigger number between 11 and 20 by a smaller number between 1 and 10.
When solving a multiplication equation, align the numbers vertically, or up and down, like this.
Here we have 11 x 8.
You'll notice that it's on a place value chart.
To know more about place value, be sure to watch the videos called, "Place Value I," and, "Place Value II."
OK, see how the 8 is under the right hand digit 1, or in the ones place?
You need to keep track of the place value when you multiply.
We need to multiply both of the digits in 11 by 8.
We work and equation like this from right to left,
so 8 x 1 is 8,
then 8 x 1 again is 8.
Did you get 88 as the answer?
Now let's try 12 x 6.
The product of 6 x 2 is 12.
We'll write 2 in the ones place, and carry the 1.
When we carry, we are actually moving a group of 10 ones to the ten place.
6 x 1 is 6, plus the 1 we've carried makes 7, for a product of 72.
Take a look at this equation.
See something new?
We're multiplying a 2-digit number by a 2-digit number.
We've lined up the place values, so the ones are in a vertical row, as are the tens.
Let's work this problem together.
First, we'll multiply the 12 by 3.
3 x 2 is 6, so we write 6 in the ones place. And 3 x 1 is 3, so we write 3 in the tens place.
It's very important to keep everything lined up, so when we are multiplying the ones column,
we put that answer in the ones place, and when we multiply the tens column,
we put that answer in the tens place.
Now, we still need to multiply 12 x 1.
For that, we need to start a new line.
But there's a trick.
We're not multiplying by something in the ones column, but by the tens column.
Because of that, we'll put a 0 in the ones column to indicate there are no ones.
1 x 12 is 12, but those numbers go into the tens and hundreds column.
We now have 36 and 120.
We need to add these two numbers together to get the final answer.
The answer is 156.
Let's practice one more.
This time, we'll do it without the place value chart, but keep in mind that the digits in
these numbers still hold a place value.
Remember, we start with the digits in the ones place, so we'll multiply 13 x 6.
3 x 6 is 18, so we'll write the 8 in the ones place and carry the 1.
6 x 1 is 6, plus 1 is 7, so we'll write the 7 in the tens place.
Before we can multiply 13 x 1, we need to put a 0 in the ones place.
Now, 13 x 1 is 13, so we'll write 13 with the 3 in the tens place and the 1 in the hundreds place.
Now we need to add 78 and 130.
The answer is 208.
You've had a chance to practice some complex multiplication problems.
We worked with numbers under 20, but the exact same methods let you multiply even bigger numbers.
Practice your multiplication skills on our fun online games and quizzes,
and remember to always be clever.