Addition Strategy

Learning Another Addition Strategy

What are we doing today?

​Today you will…

Use the strategies you learned last week to figure out the number of animals in the desert scene of 1001 Animals to Spot.

• You will also learn a strategy for adding 9 to numbers.

Let's figure out how many animals are on each of these pages.

• Let's start with the left hand page

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Open your book to pages 6-7.

Fill in the Blank

There are ____ ostriches 

Fill in the Blank

There are ____ warthogs.

Draw

Let's look at page 6. How can you use the strategy of making 10 and then adding 10 to figure out the total number of animals on the page?

Match

You know the pattern for adding 10 to numbers. Now we will look at a pattern for adding 9.

Match the following

• 10 + 3 =

• 2 + 10 =

• 5 + 10 =

• 10 + 10 =

• 10 + 1 =

13

12

15

20

11

• 13

• 12

• 15

• 20

• 11

Draw

Let's SWITCH IT UP!!! ADDING 9's

Audio Response

What did you notice about the sums that we added by 9?

Open Audio Recorder

Did you know?

One way to add 9 to a number is to add 10 and the subtract 1.

Adding 9 to a number

Here's how I think about adding 8 + 9:

• 8 + 10 = 18

• 1 less is 17( 18- 1 = 17)

Here is how I think about adding 22 + 9 :

• 22 + 10 = 32

• 1 less is 31( 32 - 1= 31)

We will read the names and numbers of the animals.

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​Let's look at page 7.

​More than one way!

I will show you one way we can add the numbers from page 7.

• I will keep track of my thinking by crossing out numbers as I use them and writing equations.

• To start I know that 6 + 8 = 14

6 10 8 9 10

​What's next?

Next, I'll add 10. How much is 14 plus 10?

6 10 8 9 10

Now I'll add the other 10. How much is 24 plus 10?

24 + 10 =

Only 9 left!

I can use the strategy for adding 9.

• I will add 10 to 34, getting 44.

  • Then take away 1.

  • How much is 34 + 10 = _____

  • How much is this number minus 1? ______

10 10

4 10

8 4

10 8

9 9

Let's Try

It helps sometimes to change the order of the numbers to make branching easier.

• I'll write the 10s together.

Let's look at page 8 of 1001 Animals to Spot

We will work as partners on WorkSpace page 3.

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What's Next???