Multiplication and Division

Multiplying 2- and 3-Digit Numbers

Stacked Multiplication Problems

When you multiply a number or amount, you're increasing it many times. In the last lesson, you learned that multiplication can be a way to understand things that happen in real life. For instance, imagine that a store sells boxes of pears. The small boxes contain five pears each. You buy two. You could write the situation like this, and use the times table to solve it:

Now, imagine that you decide to buy two larger boxes containing 14 pears each. That situation would look like this:

This problem is harder to solve. Counting the pears would take a while. Plus, there's no 14 on the times table. Fortunately, there's a way to write the problem so that you can break it into smaller pieces. It's called stacking. It means that we'll write the numbers on top of one another instead of side by side.

Let's practice stacking with this problem, 14 x 2.
First, write the numbers, one above the other. It's a good habit to always write the larger number on top. The problem will be harder to solve if you don't.
Next, write the times sign to the left of the numbers.
Instead of an equals sign, put a line underneath the number on the bottom.
Notice how the numbers are lined up to the right?
When you write a stacked multiplication problem, always make sure the numbers are lined up this way.
For example, let's look at another problem, 5 x 112. See how the 2 is right above the 5?
Also, notice that we put the larger number on top, even though it was the second number in our original expression.
Always set up stacked multiplication problems the same way: with the larger number on top...
Always set up stacked multiplication problems the same way: with the larger number on top... and the right digits lined up.