Adding by 1

Overview

You can find how many there are in all by adding two groups of objects together.

In this lesson, we will learn how to add by 1 to any group of objects.

There are many examples in real-life where you will need to use the skill adding by 1. Pretend you are having a birthday party and there are 10 people in total including you celebrating.

Suddenly, one of your friends shows up to your front door unannounced to join your birthday party. Now, we have one more meaning we need to add by 1 to find the total number of people at your party.

Now, let’s take a look at some more examples using pictures.

Let’s take a look at the example above.

There are 2 circles in the first group and there is 1 more circle in the second group.
We can ADD them. We do this by joining the 2 amounts together.

This will give us the total number of circles IN ALL.

When we ADD 2 plus 1, we have 3 in all.
We say: TWO plus ONE equals THREE.
We write it like this: 2 + 1 = 3

Here’s another example.

In this problem, we are joining together two groups of dogs.
We are ADDING them together.

This will give us the total number of dogs.

When we ADD 4 plus 1, we have 5 in all.
We say: ONE plus TWO equals THREE.
We write it like this: 4 + 1 = 5

This time, we are working with the numbers 8 and 1.
These numbers are known as ADDENDS.

Addends are the amounts that will be joined together.

This problem reads as 8 + 1 = 9.
When the ADDEND 8 is joined with the ADDEND 1, we get a SUM of 9.
The SUM is used to describe the total amount.

When we add ONE MORE to a group of objects, we can remember that the SUM will be the number that comes next when we are counting.

5 + 1 =

For example, 5 + 1 = 6. We also know that when we count, the number that comes after 5 is the number 6. This can help us to add quickly and correctly when adding 1 to a group.

12 + 1 =

Let’s try another example. What is 12 + 1? We can add or count on from the number 12. We know that the number that comes after 12 is the number 13.
Therefore, 12 + 1 = 13.

1 + 9 =

Here is another example. This time our 1 comes first and our group comes second. We can still solve in the same way. What is 1 + 9? We can add or count on from the number 9. We know that the number that comes after 9 is the number 10.
Therefore, 1 + 9 = 10.

Look at the example above. Two groups are being joined together to find the total.
5 bees plus 1 bee will tell us how many bees there are in all.
When we count, we know that the number that comes after 5 is 6.
Therefore, 5 + 1 = 6 bees.
There are 6 bees in all.

There are many different words that are used to describe addition. Take a look at the picture below to review the keywords that describe the mathematical operation – addition.

Knowing these keywords will help you understand that in order to solve the problem, you must add. All the examples above dealt with pictures.

Let’s try adding by 1 in word problems. 

In the problem, the pencils are being joined together. The key words are AND as well as ALTOGETHER. This helps tell us that we need to ADD.

ONE blue pencil is joined with THREE red pencils and this will give us the correct SUM.
We can count on one from three to help us find the answer.

1 + 3 = 4 pencils

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

Practice Question 1

 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.

1 + 8 =

REVEAL THE ANSWER

Practice Question 4

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

REVEAL THE ANSWER

Practice Question 5

Let’s try one more problem!
Look at the groups below.
How many are there in all?
Write an addition sentence and solve.

REVEAL THE ANSWER

Hooray! You’re ready to take a quick quiz on adding by 1!