Learn all about adding two-digit numbers and adding three-digit numbers in this free lesson, which includes practice problems.

### Solving Stacked Addition Problems

To solve stacked addition problems, all you need are the skills you learned in Introduction to Addition.

Let's try solving this problem, 24 + 12.

To solve a stacked addition problem, start by adding the digits farthest to the **right**.

In this case, that means we'll add 4 and 2.

Like with any addition problem, we can use **counting** to help us add. Since our first digit is 4, we'll start with four objects.

We're adding 4 to 2, so we'll use two more objects.

We can count to get a total of 6. We know that 4 + 2 = 6.

Write 6 under the line. It's important to put it directly **beneath** the numbers we just added.

Next, we'll add the digits to the **left** of the ones we just added. That's 2 and 1.

We'll use two objects to show the 2.

Next, we'll add one object to represent the 1.

When we count, we get 3.

We'll write the 3 under the line, beneath the 2 and 1.

We're done! Our total is 36, or thirty-six.

Let's look at one more problem, just for practice. This time, we'll solve 62 + 5.

We'll start by adding the digits on the right, 2 and 5.

2 + 5 is 7.

Now, let's add the digits to the left. The top digit is 6, but there's nothing beneath it.

6 plus nothing is 6, so we'll write a 6 below the line.

Our total is 67, or sixty-seven.

As you saw, stacked addition problems are always solved from **right ****to left**. This means that you always start by adding the digits on the **right**.

#### Try This!

Solve the addition problems below. Then, check your answer by typing it into the box.

#### Adding Very Large Numbers

Stacked addition can also be used for adding **larger numbers**. No matter how many digits are in the numbers you're adding, you add them the same way: from right to left.

Let's try adding two **3-digit **numbers. We'll complete this expression: 213 + 406.

As always, we start with the digits on the **far right**. Here, that means we'll solve 3 + 6.

3 + 6 is 9, so we'll write 9 directly beneath the 3 and 6.

Next, we'll add the digits to the **left** of the ones we just added, 1 and 0.

1 + 0 is 1, so we'll write 1 below the line. Make sure to put it** directly beneath** the digits we just added, to the **left** of the 9.

Finally, let's add the next set of digits, 2 and 4.

2 + 4 is 6. Let's write the 6 beneath the line, under the 2 and 4.

The problem is complete. Our total is 619, or six hundred nineteen. 213 + 406 = 619.

#### Try This!

Add these large numbers. Then, check your answer by typing it in the box.