Adding by 10

Overview

How many fingers do you have in total? We have ten fingers and in this lesson, we are going to master the skill of adding by 10.

In previous lessons, we talked about adding by 1, 2, 3 and 5. I’ll share a secret with you! Adding by 10 is my favorite because it’s actually very easy.

Let’s start learning by looking at the picture below.

Here is an example. Let’s take a look!

There are ten suns in the first group and 8 more suns in the second group.
We can ADD them by joining the two amounts together.

This will give us the total number of suns.

When we ADD 10 plus 8, we have 18 in all.
We say: TEN plus EIGHT equals EIGHTEEN.
We write it like this:

10 + 8 = 18

In this problem, we are joining together two groups of raindrops.
We are ADDING them together.
This will give us the total number of raindrops.

In the picture above the first group has 4 raindrops and the second group has 10 raindrops. We need to ADD 4 plus 10. BUT here is a very big secret!

Instead of writing the problem as 4 + 10, let’s switch the two numbers and make it 10 + 4.

By doing so, we only need to COUNT UP 4 from the number 10.

In the original problem 4 + 10, some students may COUNT UP 10, but this is a waste of time. Always use the bigger number and count up using the smaller number.

When we ADD 10 plus 4, we have 14 in all.
We say: TEN plus FOUR equals FOURTEEN.
We write it like this:

10 + 4 = 14

Let’s take a look at another example with numbers.

This time, we are joining the numbers 2 and 10.
These numbers are known as ADDENDS.

Addends are the amounts that will be joined together.
This problem reads as

2 + 10 = ?

We can re-write this problem as

                     10 + 2 = ?

When the ADDEND 2 is joined with the ADDEND 10, we get a SUM of 12. Simply count up 2 from the number 10.

When we add TEN MORE to a group of objects, we can remember that the SUM will be the number that is TEN more than that number.

10 + 5 =

For example,

10 + 5 = 15.

We also know that when we count up, the number that comes ten after 5 is the number 15. The number in the ones place stays the same, and the number in the tens place changes by one. This can help us to add quickly and correctly when adding 5 to a group.

3 + 10 =

Let’s try another example.

What is 3 + 10?
We can join the two groups by adding ten to 3.
Therefore,

3 + 10 = 13.

5 + 10 =

Here is another example. What is 5 + 10? We can add or count on five more from the number 10. This time, draw a picture to solve. Make a group of five objects and another group of 10 objects. Then count them altogether to find the total. When we solve, we will find out that

5 + 10 = 15.

Look at the example above. Two groups of stars are being joined together.
We can count the pictures to help us add.
4 stars plus 10 stars will tell us how many stars there are in all.
4 stars + 10 stars = 14 stars in all.
There are 14 stars in all.

Just like the previous lessons, let’s review the keywords again that help us identify when to use the addition operation. These are words you should be familiar with and when you see them in a word problem, you will know that you need to add.

Knowing these keywords will help you understand that in order to solve the problem, you must add.

Let’s try adding by 10 in story problems.

In the problem, we want to find out how many melons there are now. To solve, we need to add.

TWO melons combined with TEN melons will give us the correct SUM.

We can draw and count to help us find the answer.
Draw a picture to go with the problem. Then solve.

2 + 10 = 12 melons

There are many additional strategies you can use to help you add correctly. We will continue to learn about these in other lessons.

Practice Question 1

Let’s practice! Write the addition sentence and solve the problem below.

REVEAL THE ANSWER

Practice Question 2

 Write the addition sentence and solve the problem below.

REVEAL THE ANSWER

Practice Question 3

Take a look at the math sentence below. Draw a picture to match it. Then solve.

10 + 5 =

REVEAL THE ANSWER

Practice Question 4

Look at the groups below.
How many unicorns are there in all?
Write an addition sentence and solve.

REVEAL THE ANSWER

Practice Question 5

Look at the animals below.
How many animals are there in all?
Write an addition sentence and solve.

REVEAL THE ANSWER