Bài 10: Addition using number – line

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 https://www.youtube.com/watch?v=n-t2nLgBLD0

Starry, do you remember these number beads.

We use them to make a number line.

Let us put them together and make one again.

The first bead will be 0 then 1-2-3-4-5-6-7-8-9 and 10.

Wow Starry, a number line. 

But Starry, we can also draw the number line like this.

We draw the straight horizontal line with arrows on both sides.

We start from 0 and then write the number at equal distances like this.

0-1-2-3-4-5-6-7-8-9 and 10.

Starry, the number line can be useful to us in many ways.

Today I will show you how to add using the number line.

Suppose we have to add 3 plus 1.
Look at the number line begin from 3, move 1 place to the right.

What number do we reach Starry?

Yes, the number 4. So 3 plus 1 equals 4.

Next we will add 2 plus 3.

Start from 2 move to 3 places to the right 1-2-3, we reach the number 5. So 2 plus 3 equals 5.

Wasn’t that easy Starry?

And now Starry, 3 plus 4.

We start from 3 and we move 4 places to the right 1-2-3-4, we reach the number 7.
So 3 plus 4 equals 7.

Now Starry shall we do an activity together.

We have the first add the objects by counting them.

We have to  next add the same objects using the number line.

Let’s begin with the butterflies.

1-2-3-4-5 butterflies plus 1-2 butterflies.

5 plus 2 that's 1-2-3-4-5-6-7 butterflies. So 5 plus 2 is 7.

Now on the number line 5 plus 2.
We start at 5, we move 2 places to the right 1-2.

We reach the number 7. So 5 plus 2 equals 7.

Next we have bows Starry. 
1-2-3-4 bows plus 1-2-3-4 bows.

4 plus 4 that's 1-2-3-4-5-6-7-8 bows. 4 plus 4 equals 8.

On the number line 4 plus 4.

We start at 4 and move 4 places to the right .
1-2-3-4 we reach the number 8.

So 4 plus 4 equals 8.

Let us  now count the leaves Starry?

1-2-3 leaves plus 1-2-3-4-5 leaves.

3 plus 5 leaves that is 1-2-3-4-5-6-7-8 leaves.
3 plus 5 equals 8.

Now the number line 3 plus 5, start from 3 move 5 places to the right 1-2-3-4-5, we reach the number 8.

So 3 plus 5 equals 8.

What do we have here some flowers ,Starry!1-2-3-4 flowers plus 1-2-3-4-5 flowers.

4 plus 5 flowers is 1-2-3-4-5-6-7-8-9 flowers. 
4 plus 5 equals 9.

Let us now add on the number line. Start at 4 move five places to the right. 1-2-3-4-5 we reach the number 9. 4 plus 5 equals 9.

Finally, stars 1-2-3-4-5-6 stars plus 1-2 stars, 6 plus 2 equals 1-2-3-4-5-6-7-8 stars.6 plus 2 equals 8.

Now on the number line, 6 plus 2 start at 6 move 2 places to the right 1-2 we reach the number 8.

So 6 plus 2 equals 8.

Excellent, you have now learnt to add on the number line.

So Starry, remember the number line is very useful to us, it helps us with our addition

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