Lesson 3 of 7
Objective: SWBAT retell missing addend story problem and use color as a scaffold.
Objective & Hook
We have worked on all kinds of story problems this year. Today we are going to look at a problem where we have to identify the missing part. We need to figure out what is missing in the story.
Great mathematicians can solve all sorts of story problems. They retell story problems in their brain or with a partner to help them solve the stories!
Objective: I can retell a story and identify what part is missing.
Ms. Poe has 5 blue crayons and some red crayons. She has 9 crayons in all. How many red crayons does she have?
- What information did the problem tell us?
- What information was missing?
- What is it my job to figure out?
Let’s write a number sentence to match. When we get to the part we don’t know, we are just going to draw a box. The box means we have to figure out that part.
- First, we had 5 blue crayons, so I’ll write 5 in blue. Then we had some red crayons. Do I know how many? So we’ll write a red box to represent the number of red crayons. And last we have 9 crayons in all-this number sentence should be the same as having 9.
- So my number sentence is 5+some more is the same as having 9. 5+____=9
Partner talk: How could we solve this problem? Because the numbers are so small, this process will be surprisingly intuitive for a lot of students. Many of them will already know the answer to the problem.
Whole Group Model: I’ll have students quickly share out their strategies for solving this problem. Watch the attached Strategy Share video to see one student share out a counting on strategy and the questioning I use to make sure he and the rest of the class understand the strategy.
Partner talk: What was missing in this story problem? Why did Ms. Cole put a red blank in the number sentence?
There are 10 yellow crayons in the basket. We get some blue crayons. Now there are 14 crayons. How many blue crayons did we get?
- Retell the story with a partner. What are we trying to figure out? How many at first/How many next or how many at the end?
- What do we need to figure out in this story problem?
- What strategies might you use to solve?
Student Work Time:
Students work for 5-10 minutes. Students need to include a strategy, words to explain their thinking and a number sentence. The number sentence at this point is mostly formative data, it will help show you what they already understand about writing a matching equation! Having students write their strategy is a way to help them truly internalize their own strategy. It also addresses the CCSS emphasis on writing across the curriculum.
- Show 2 strategies. One of the strategies should be a student who modeled the problem with cubes. The other one should be a counting strategy.
- Partner talk after each one: How did this person figure out how many blue crayons?
- What number sentence matches this story?
- Let’s retell the story using the number sentence: First there were 10 yellow crayons. Then we got 4 more blue crayons. At the end, there were 14 crayons.
Group A: Intervention
Students solve 2 missing addend problems with very low numbers. Because this is a new type of problem, these students may need numbers under 10 to start with.
Group B: Right on Track
Students solve 2 problems with mid range numbers. (numbers under 20)
Group C: Extension
Students solve 2 problems-Students need to write the missing addend number sentence. To push your highest kids, have the first number be the one that is missing. Start unknown problems tend to be harder (numbers under 50).
Teacher writes in the numbers for each group. See attached Colorful Story Problems.
Choose one student to share their strategy with a class. Have students turn and talk to explain the strategy.