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# 2.2: Straws and Glasses

Difficulty Level: At Grade Created by: CK-12

Can you draw 5 in each glass? Then can you count to figure out how many straws in all? Can you count by 5s? In this concept, we will practice drawing straws and then counting by 2s or 5s to figure out how many we have.

### Guidance

Once you have drawn in straws like in the problem above, there are many ways to count how many we have. Since there are 5 straws in each glass, one way to count all of the straws is to count by 5s. If we put 2 straws in each glass, we could count all of the straws by counting by 2s.

#### Example A

Look at the picture below:

Draw 2 in the glass.

Your picture should look like this:

Count the straws. How many straws in all?

You should see that there are 2 straws in all.

#### Example B

Look at the picture below:

Draw 2 in each glass.

Your picture should look like this:

Count the straws. How many straws in all?

You should see that there are 4 straws in all. We can count by 2s ("2, 4") to get our answer.

#### Example C

Look at the picture below:

Draw 2 in each glass.

Your picture should look like this:

Count the straws. How many straws in all?

You should see that there are 8 straws in all. We can count by 2s ("2, 4, 6, 8") to get our answer.

#### Concept Problem Revisited

Once we draw 5 straws in each glass, our glasses look like this.

We can count by 5s to figure out how many straws there are in all. When we count like 5s it sounds like "5, 10, 15." There are 15 straws in all.

### Vocabulary

Counting by 2s is when you count objects in groups of 2. When you count this way, it sounds like "2, 4, 6, 8, 10, ...". Counting by 5s is when you count objects in groups of 5. When you count this way, it sounds like "5, 10, 15, 20, 25, ...".

### Guided Practice

Draw 5 in each glass. Count the straws. How many straws in all?

1.

________________ straws in all

2.

________________ straws in all

3.

________________ straws in all

1. There are 5 straws in all.

2. There are 10 straws in all.

3. There are 20 straws in all.

### Practice

Draw 2 in each glass. Count the straws. How many straws in all?

Draw 5 in each glass. Count the straws. How many straws in all?

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Date Created:
Jan 18, 2013
Mar 23, 2016

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