SWBAT apply known facts to solve other number sentences.

How can 30+30 help you solve 30 + 31? That question drives this lesson as students make connections between number sentences.

5 minutes

**Hook:**

We are going to be solving story problems about butterflies today in math! Watch this nonfiction video about butterflies. Go to this National Geographic link for the video! One of the CCSS shifts in ELA is increasing informational text exposure to support students’ content knowledge and ability to navigate these texts. That includes visual media like video!

**Objective:**

Your thinking job is: How can I use a fact I already know to help me solve another number sentence?

10 minutes

**Present Problem: While I was playing outside, I found 30 caterpillars and put them in my bug box. Then I found 30 more caterpillars and put them in my bug box. How many caterpillars are in my bug box?**

**Partner Talk: How could we solve this problem really quick?**

- At this point, most students will probably be very used to solving these and be fairly comfortable with them.

I'll choose a few students and quickly chart how they solved it.

**Partner Talk: Share what this person did to figure out there are 60 caterpillars.**

- This partner talk allows students to explain someone else's thinking, which is the foundation of them being able to "critique each other's reasoning", CCSS MP3.

**Present 2nd problem: I'll have this second problem on the same piece of chart paper so students can explain both.**

**The next day I was playing outside, and I found 30 caterpillars again! I put them in my bug box. Then, I found 31 more caterpillars and put them in my bug box. How many caterpillars did I find?**

Guiding Questions: This problem pushes students to "Look for and express regularity in repeated reasoning" (CCSS MP8). Students are looking for similarities across problems and creating mental bridges between kinds of problems.

- How is this problem the same as the first problem?
- How is it different?
- Could we use the first problem to help us with the second?

20 minutes

At your desks, you are going to solve the second problem. I want to see what strategies you can use to solve this problem quickly.

**As you are working, think about: Could I use what I know from the first problem to help me with the second problem?**

**Work Time:** Students work for 7-10 minutes on this problem.

**Student Share Time:**

*Bring students back together and share out strategies. A few kids might revert back to an old strategy that doesn’t get them to an answer quickly! If they do this, don’t worry. Seeing the strategies their peers use will help them get back to more sophisticated strategies.*

**Partner Talk: Share with your teammate how you solved this problem.**

I'll have a student who applied 30+30 to share how they solved. This student most likely built two groups of 30 with base ten blocks and then added 1 extra one. If time, I'll also have a student who just added 60 + 1 share their thinking.

**Guiding Questions:**

- Why did you use a ones block? Why didn’t you make another 10?
- How did you count them? Why didn’t you count this one as a 10?
- How did you know that you just needed to add 1 more? Did you use cubes or numbers?
- How did the first problem, 30+30, help you with 30+31?

**Partner Talk: How did this student solve this problem? **

15 minutes

Students solve 3 problems. The first 2 problems will be similar to the student share problems. I'll choose sets of numbers where students can apply the first story to the second one. The last problem is always subtraction. This helps insure that students always pay attention to what is happening in the problem and that they don't just add them out of habit.

**Group A: Intervention**

For now, these students stay on the decade. They should be working with numbers under 50.

**Group B: Right on Track**

Students work on numbers under 100. The first story problem may be 40 + 40. The second would be 40 + 42. I'll have the subtraction problem be a related fact, such as 70 - 30.

**See attached video of a student explaining how 40+40 helped her solve 40 + 42!**

**Group C: Extension**

Students work on numbers under 100. In their problems, they start with 40 + 31, and then the second problems is 42 + 31. These students are ready to think more about the ones place then the other groups.

**See attached story problems!**

I left the numbers blank so teachers could write in numbers that work best for their students.