## Student's Guess and Check strategy - Section 4: Independent Practice

*Student's Guess and Check strategy*

# Who Stole the Cookies?

Lesson 4 of 7

## Objective: SWBAT identify the missing subtrahend in a subtraction story problem.

#### Setting Up the Learning

*10 min*

To hook students in, watch the video of the story "Who stole the cookies from the cookie jar?" This moving picture story is colorful and fun!

**Review:**

We worked on figuring out how many animals went in the circus tent in yesterday's lesson. Today we are going to keep thinking about the missing part of a subtraction story, but we are going to use the Cookie Jar game to help us!

**Connect:**

This is important because sometimes we need to figure out how many we lost. One time, I was trying to put together a puzzle, but I lost some of the pieces! I had to figure out how many were missing.

**Objective:**

What strategies can I use to solve missing part problems?

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#### Opening Discussion

*10 min*

My chart paper of the day will have the lyrics to the song we are going to use - it is an easy opportunity to put in some reading fluency practice (RF.1.4: Read with sufficient accuracy and fluency to support comprehension) and aligns to the Common Core vision of literacy across the curriculum.

When we play the "Who stole the cookies" game today, we are going to change the words. This is to the tune of the original song, which you can listen to here.

**How many did you steal from the cookie jar? **

**Who me? ****Yes you!**

**Beats me! **

**We'll get you!**

I'll model one round. I'll just use cubes or counters to represent cookies. In my model, I'll count out 20 cookies into the cookie jar in front of students. This helps them "trust" that there are 20 to start with and use that as a starting point of there thinking later.

**How the game works:**

1. Count out 20 cookies.

2. Other students close their eyes.

3. The "stealer" steals some cookies.

4. Everyone counts how many are left over and figures out how many are missing. (after singing the song!)

I'll take away 5 and have students try to figure out how many I stole. I'm intentionally seeing if they can figure out how many I stole without having any cubes. I want to challenge them to do it mentally.

**Partner talk: What could you do to figure out how many Ms. Cole stole? **

- Possible strategies: Count on from 15 to 20, Count back from 20 to 15, use the number line and count the jumps

I'll quickly chart how 1 student figured it out and then have the class check to see if that student is correct.

I'll also record a number sentence to match. As I record the number sentence, I am helping students "Reason abstractly and quantitatively," CCSS MP2. See below how I connect the numbers to the concrete so students understand how we are representing the concrete experience in numbers.

*The key thing to emphasize here is where the answer is to our question. To help with this, you can go through each number in the number sentence 20- 5 = 15. "20 is how many we have at first. 5 is how many we took away. 15 were still in the jar. My question was "how many did Ms. Cole steal", so the answer to the question is 5."*

**Partner talk: How many did Ms. Cole steal? How did ___ figure it out?**

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#### Student Work Time and Share

*15 min*

**Whole Group Game Play: Watch a video of one student playing the game! **

We will play the game a few more times on the rug, choosing different "stealers:" Hiding the Cookies! Each time we play and sing the song, I'll have students do a partner talk to explain how many that person stole. I will keep the start point consistent at 20.

After each round, I'll model the missing part number sentence, specifically discussing how the answer to our question is in the box in the middle of the number sentence.

I'll also listen to the partner talks for different strategies to add to the initial strategy I charted in the Opening Discussion. Keeping a "log" of strategies will help students try out different, more efficient strategies. It will also provide a mental road map of how to think through this kind of problem for students who are struggling with the concept.

**Student Work Time and Share:**

**After we play a few more rounds, I'll do one where students have to go write down how many I stole and how they know. This promotes independence, a key component of the Common Core, and will also prepare them for the Independent Practice.**

After students work for 5-7 minutes, I'll have them share how they solved with a partner.

#### Resources

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#### Independent Practice

*15 min*

To invest students and encourage some creativity, I'll have students "choose" who stole the cookies in their story problems. First graders love to write each other's names. To make this a seamless process (and avoid the constant talking about "How do you spell your name?"), I'll put a list of student names on the board.

**Group A: Intervention Groups**

Students solve with numbers under 10 if needed. 10 is a good starting point because we have 10 fingers! :)

**Group B: Right on Track**

Students solve story problems, record a number sentence and write how they solved. Numbers under 25.

- One strategy students might try to use is "guess and check". I attached a video, Student's Guess and Check strategy, of 1 student trying this out. She was just taking away cubes until she thought she got to 11. My next step with this student is to have her separate the 11 that she knows and keep them in the "jar". This would help her directly model the problem without have to guess.

**Group C: Extension**

Students get numbers under 75.

**See attached story problems: Cookie Stealing Story Problems.**

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#### Closing

*5 min*

**Bring students back together. Push students to apply what they did in their own story problems to a number sentence, which is aligned to CCSS MP2, Reason abstractly and quantitatively. This helps students contextualize the numbers that they see, without having the support of the story problem. **

Let's see if we can create a Cookie Stealing story problem for this number sentence:

15 - ____ = 13

**Guiding Questions:**

- What does the 15 represent?
- What does the 13 represent?
- What does the blank represent?

Write a story problem as a class to match this number sentence and solve!

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- UNIT 11: Missing Parts: Unknowns in All Positions
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