Addition Within 10: math lesson, Grade 1

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Math lessons Grade 1 : Addition Within 10 — Zyro the alien explorer of Planète Maths

Welcome, Grade 1 mathematician! In this chapter you will learn how to add. Adding helps you find out how many things you have when you join two groups. You will use small numbers, from 0 up to 10. Let’s get started!

Sommaire

1. Adding means putting together

Imagine you have 3 red counters on one side of your desk and 2 blue counters on the other side. Now you slide them next to each other. How many counters are there in all? You count: 1, 2, 3, 4, 5. There are 5 counters.

When you put two groups together to find the total, you are adding.

Definition: adding

Adding means finding how many there are in all when we join groups. The answer to an addition is called the sum (or the total).

2. Adding means adding to

There is a second way to think about adding. Some things get more. A story starts with one group, and then more arrive.

Example 1: birds on a wire

4 birds sit on a wire. Then 3 more birds land on the wire. How many birds are on the wire now?

We start with 4 and add 3 more. We count on: 5, 6, 7. The answer is 7 birds. In numbers: \(4+3=7\).

Putting together and adding to look different in a story, but both use the same math. Both are written with a plus sign.

3. The plus sign and the equal sign

Mathematicians use two special signs.

The plus sign \(+\) means “add” or “and more.”
The equal sign \(=\) means “is the same amount as.”

Definition: equal sign

The equal sign tells us that what is on the left has the same value as what is on the right. It is like a balanced seesaw.

So \(3+2=5\) says that “3 and 2 more” has the same value as 5. Read it out loud: “three plus two equals five.”

Be careful!

The equal sign does not mean “the answer comes next.” Both sides must have the same value. For example, \(4+1=2+3\) is true, because both sides are 5.

4. Writing addition sentences

A number sentence about adding is called an addition sentence. It has the parts below.

First number	Plus sign	Second number	Equal sign	Sum
6	\(+\)	2	\(=\)	8
1	\(+\)	4	\(=\)	5

Method: write an addition sentence from a story

Find the two numbers in the story.
Write the first number, the plus sign, and the second number.
Write the equal sign.
Find the sum and write it after the equal sign.

Example 2: pencils

Ana has 5 pencils in her bag and 2 pencils on her desk. How many pencils does she have?

The numbers are 5 and 2. We write \(5+2=7\). Ana has 7 pencils.

5. Adding with objects and drawings

You do not have to do adding in your head right away. You can use objects like blocks, buttons, or counters. You can also draw circles or dots and count them.

A ten frame is a helpful drawing. It has 10 boxes in two rows of 5. Here, 6 orange counters and 3 blue counters are on the frame. The empty box shows that the total is just one less than 10.

Count the counters: 6 and 3 more make 9. We write \(6+3=9\).

You can also use a number line. Start at the first number, then hop forward the second number of steps.

Example 3: hop on the number line

To find \(4+3\), start at 4. Hop 3 steps: 5, 6, 7. You land on 7. So \(4+3=7\).

6. Number bonds for 10

A number bond shows a whole number split into two parts. The number 10 is very special. Knowing all the ways to make 10 will help you for many years!

Number bonds for 10

These pairs of numbers make 10 when you add them.

Part	0	1	2	3	4	5	6	7	8	9	10
Other part	10	9	8	7	6	5	4	3	2	1	0

Tip from Zyro

“On my planet we make 10 with our fingers. If 7 fingers are up, then 3 fingers are down. So \(7+3=10\)!”

7. Adding zero

Zero means none. What happens when you add none? Nothing changes! If you have 5 apples and you get 0 more apples, you still have 5 apples.

Adding zero

When you add 0 to a number, the number stays the same. For example, \(5+0=5\) and \(0+8=8\).

Be careful!

Adding 0 does not give 0. The sum of \(6+0\) is 6, not 0. Only \(0+0\) equals 0.

8. Changing the order: turn-around facts

Here is a surprising fact. When you add two numbers, you can swap them and the sum stays the same. Look at the two groups of counters below.

Turn-around facts (commutative property)

You can add two numbers in any order. The sum is the same. For example, \(2+5=5+2=7\).

This is a big shortcut. If you know \(3+6=9\), then you also know \(6+3=9\). You learn two facts for the price of one!

Tip: when one number is bigger, start with the bigger number and count on. For \(2+7\), think \(7+2\): start at 7, then count 8, 9.

9. Check your work and practice

Good mathematicians always check their answers. After you add, ask yourself: is my sum bigger than both of the numbers I added? It should be, unless you added 0. Then draw the counters or count on a number line to see if you get the same total.

Try a game with a friend. Roll two dice, add the dots, and say the addition sentence out loud. For example, if you roll 3 and 4, you say “3 plus 4 equals 7.” Then swap the numbers and say “4 plus 3 equals 7.” Practice a little every day and the facts will soon feel easy.

Key takeaways

Adding means putting groups together or adding more to a group.
The plus sign \(+\) means add. The equal sign \(=\) means “has the same value as.”
An addition sentence looks like \(3+4=7\). The answer is called the sum.
You can add with objects, drawings, ten frames, and number lines.
Number bonds for 10 are pairs such as \(4+6\), \(3+7\), and \(5+5\).
Adding 0 does not change the number: \(8+0=8\).
You can swap the numbers: \(2+5=5+2\).