SWBAT solve a 3 addend number sentence by combining 2 addends.

Incorporate both 1.OA.1's Make 10 strategy focus AND 1.OA.A.2's focus on adding 3 addends as students work to solve word problems.

10 minutes

**Hook:**

I'll start by doing Quick Images, a quick subtilizing within 10 game. The game is listed first as Numbers to 10 on the Ten Frame. This online tool is free and excellent for helping students build fluency with numbers that add to ten, and also helps them use base 5 to subitize quickly. I use this routine throughout the year to help students build a strong number sense!

- Frame it for the kdis:
*When people add and subtract numbers in their brains, they use really friendly numbers-numbers that are easier to add and subtract with. 5 is friendly but 10 is your best friend! We are going to play a quick game to get our brains thinking about using friendly numbers to add and subtract.*

Every time I show one, I show it for 2-3 seconds. I usually show it twice, at about 2 seconds each, then I call on one student to tell me how many and quickly to tell me how they know. Then I ask the question: How many more to make 10?

**Objective:**

We know lots of number facts in our brains by now-we just found all these ways to make 10! Today you are going to see if you can use number facts to help you solve problems quickly.

**Your thinking job today is: What strategies can I use to make it easier to add 3 numbers? What friendly number sentence is hiding in that number sentence? **

10 minutes

**Present Problem: A little girl named Elizabeth went to the store. She bought a bunch of candy. She bought 5 lollipops, 5 chocolates and 3 pieces of bubblegum. How many candies did she buy in all?**

I’ll have one student model for now, using a different color of cube for each type of candy.

**Guiding Questions:**

- Let’s look at these cubes. Does anyone see 2 numbers we could put together so we could make this number sentence easier?
- ___, why do you want us to put together 5 and 5? Yes! 5+5 is so friendly! We know 5+5 is so easy so we can start with that. (Have student model with cubes)
- But are we done? Is the answer to this story problem 10? Why not?
- Do we need to count all the cubes? No! We can start at 10 and count on. We already know 5 and 5 is 10, and then we can say, count with me, 10, 11, 12, 13.

**Let’s write what we just did on our strategy chart so we can look back to it in a minute. While I’m writing, tell your partner. How did we solve this problem?**

See attached Strategy Chart.png for how I present this to kids. The circle under 5+5 is what I call a "bunny". We talk about how we can put 5+5 together, draw bunny ears and then write 10 in the bunny.

- This discussion is aligned to MP8, Look for and express regularity in repeated reasoning. As students solve, they are proving the associative property over and over-we can put the addends in any order and combine then in any order. As they continuously prove this, they start to realize that this is a "shortcut" or a strategy that can always work when they are adding.

After I draw the strategy chart, we will retell the strategy as a group.

15 minutes

For the student share time, students will work with a partner. Each partner group needs 3 towers of* *cubes; each tower is a different color. They also need a double ten frame. Mathwire has one for free!

- The color helps students keep the number separate in their model, but then also helps them see reciprocity with the numbers: 7 and 3 can be put together to make 10, but 7 is still intact within 10 and so is 3. This is a crucial number sense understanding for young children!
- The double ten frame reinforces concepts of base 10, which is the HUGE focus of first grade!

**Present Problem: I’ll do as many problems as I have time for. For each problem, students will determine together what color will represent each part of the problem.**

- In the library, there are 8 No David books, 2 Dr. Seuss books and 4 animal books. How many books are in the library?
- Brittany has 7 pens, 3 pencils and 2 markers. How many does she have in all?
- The classroom has

**Guiding Questions after each problem:**

- What is the 3 addend number sentence?
- How did this friendly number sentence help us solve the 3 addend number sentence?
- Why did you choose to put those 2 numbers together?
- Are these number sentences equal? Ex: Does 5 + 5 + 3 equal 10 +3?
*This question spirals 1.OA.7, which asks students to determine if equality statements are true or false.*

** Watch this student explain how we solved 8+2+4!** You can also check out the Strategy Chart to see how we made a bunny after his share.

15 minutes

Students get 3 story problems to solve. Most students, because this is the first day of this work, will need the first set of problems, with sums under 20.

**Intervention idea:** Provide a double ten frame for students to use during problem solving. It will help them see how they could group two numbers into a ten.

**Extension problems:** These problems will probably be for very few students. Students in this group apply understandings of base ten to group larger numbers. These are students who are consistently using mental math to add numbers on the decade!

**Watch one student explain how she solved the extension word problems!**

Word problems are attached!

5 minutes

Students share one problem with a partner. Student explains how he/she solved, particularly focusing on if a friendly number sentence was used!

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