SWBAT solve missing part story problems with unknowns in all positions.

Incorporate dramatic play into your math block with this imaginative lesson! Students pretend they are taking orders in a bike shop-with each problem they have another missing part to find!

5 minutes

Students in first grade become flexible problem solvers by practicing interpreting story problems and representing them. In this lesson, students get a variety of problems to make sense of and represent numerically. Students particularly pay attention to what the missing part is, and how to show that in the number sentence. Mathematically proficient students can take the action of the problem, locate the missing portion and use a symbol to show that the quantity is unknown (CCSS MP2).

**Review & Connect**

Yesterday we played a fun game where we looked for how many cookies we started with before someone stole some! Today we are going to mix all of our different missing numbers together and we are going to use some story problems to help us use strategies to figure out what number is missing.

**Objective**

Your thinking job is: **How do I figure out what part of the story is missing and then use strategies to figure out the missing part?**

**Hook:**

Today I want us to play a game where we are pretending we are at a workshop. We are going to get lots of orders that come in from our boss that we have to fill. For example, it might say make 5 bikes and then make 4 scooters, and we have to figure out how many to make in all. Or it might say make 5 bike and make some more scooters, you need 10 in all! And we would have to figure out how many scooters. We are going to be figuring out what action (adding or subtracting) we have to do to figure out the missing part.

15 minutes

*I'll choose one student to be the "Boss" who sends down the orders. I make a station with the orders so students feel very official bringing them to me! The Bike Shop Orders.docx are attached.*

**First order just came in!**

**We need 8 red bike and some blue bikes. We need 14 bikes total.**

**Guiding Questions:**

- Hmmm…what does the boss want us to make today?
- What do we know about what he wants? What do we not know?
- What number sentence could I write to match this order? Why do we need a plus sign? Why did I put a blank here? What does the blank mean? What does the 14 mean?

**Partner talk:** How can we figure out what goes in the blank?

I’ll choose 2 students to share out their answer and how they did it! I’ll chart their strategies, focusing mostly on counting and number line strategies because I want to support students moving from concrete modeling to abstract strategies (MP2) at this point in the unit.

**Another order just came in!**

**You made some bikes. You sent 8 bikes back to the shop to be fixed. We have 11 left.**

**Guiding Questions:**

- What do we not know in this problem?
- Who can retell what we know first, next and last?
- What number sentence matches this story problem? What operation did we need, + or -? Why subtraction?
- Where did the blank go for the missing number? Why did it go in the beginning? Will that number be bigger than 6 or smaller than 6? Why?

I’ll write the number sentence and have students solve on whiteboards.

**See attached video for some examples of how students solved on their whiteboards. **You will see that kids have the freedom to choose a strategy and represent it on their own, which helps support independence and student ownership. Students don't watch me solve it and then copy-they do it all on their own!

15 minutes

Another order just came in! While we fill this order, remember our thinking job for today: Your thinking job is: **How do I figure out what part of the story is missing and then use strategies to figure out the missing part?**

**We need some red bike and 9 blue bikes. We need 16 bikes in all.**

Guiding Questions: These questions help students plan their strategy for when they go to solve it on their own!

- What do we know in this problem? What do we not know?
- What number sentence would match this problem?

I'll send students to desk to show the number sentence that matches and show the strategy they use to solve. Students will probably need 5 minutes to solve.

**Student Share:**

- Why did you use addition?
- What part do we not know? Why did you put the blank in the middle? How did you solve the story problem?
- How is this different from the other orders?

15 minutes

Students solve problems with unknowns in all positions. I differentiate their problems based on what strategies they are using to solve.

**Group A:**Relying on cubes and concrete models to solve- These students solve problems with numbers under 10.
**Group B:**Using cubes but mostly counting to solve- These students solve problems with numbers under 20.
**Group C:**Using mental math to solve almost all problems- These students get multistep story problems.
- This extends their learning towards the 2nd grade standard, CCSS 2.OA.A.1, which states that students should be solving 2 step word problems.

Bike Shop Problems.docx are attached; this includes problems for all 3 groups!

5 minutes

Students come back together and share their best work to another student. Sometimes I choose which problem students will share and sometimes I let them choose. Letting them choose is a great time to increase student investment-they are proud of the work they did!

After students share, I'll also close out the dramatic play aspect: “Good work, today. Time to close up shop” or something to that effect. This keeps the lesson fun from start to finish!