Two-Step Word Problems (Result Unknown)
Lesson 6 of 13
Objective: SWBAT solve two-step word problems using addition and subtraction strategies.
I hand out an entrance ticket (or write this problem on the board and have students solve in their math journals).
Jerry has 315 baseball cards. His dad gives him 765 more baseball cards. How many baseball cards does Jerry have now?
When finished solving, I ask students to come together and share with a partner how they solved this problem and why they chose their strategy. I then go over the problem with the class and check for any major misunderstandings with result unknown problems.
Introduction to New Material
Now I have a new question for you! We are going to use our work from the first problem to help us solve this second problem.
Jerry gives 96 baseball cards away. How many does he have now?
Turn and Talk: What should we do to solve this problem?
Students might suggest subtracting 96 from the total or subtracting 96 from one addend and then adding the last addend.
As student share their strategies verbally, I model their strategy on the board using mathematical language (equations and/or open number lines). If there are multiple student strategies, it is okay to model it two or three times so that students can clearly see multiple ways to solve this problem—have students give oral directions as you model OR have a student model his/her strategy.
Now, you are going to have a chance to work on a two-step word problem all by yourself. Just like we did as a class, you are going to use your answer from the first problem to help you solve the second problem. Make sure that you are using a strategy that allows you to be accurate in your work.
I have students work independently or in pairs on the guided practice problem for 6-8 minutes. As students work, I circulate to identify trends and misconceptions as well as to ask guiding questions: Why did you choose that strategy? What is your next step? Why did you choose to add? Why did you choose to subtract?
When students have finished working, I bring the class back together and have two students who solved the problem in different ways share out their work under the document camera or at the front of the room. Make sure that as these students model they are clearly explaining their thinking so that every student in the room understands what they are saying.
Students will work in leveled groups for independent practice:
In these types of problems, students oftentimes struggle with whether to add or subtract. Additionally, at this point in the year, some of my students also struggle with adding and subtracting using regrouping and have various levels of comfort with numbers 100-1000. Since this lesson aims at working on multi-step word problems and deciding whether to add or subtract, I want every student to be able to be challenged to solve the multi-step word problems. Thus, in order for all of my students to be able to access the material I differentiate by giving students in groups A, B, and C different sized numbers. Since students in group A are likely still using cubes bundled in tens or base ten blocks they have smaller numbers and have less regrouping. Groups B and C have larger numbers since these students are more likely to be able to feel comfortable with these kinds of numbers and need practice regrouping.
Group A (In need of intervention):
Two-step word problems using numbers 100-500 with little or no regrouping.
Group B (Right on track!):
Two-step word problems using numbers 100-800 WITH REGROUPING
Group C (Extension):
Two-step word problems using numbers 100-1000 WITH REGROUPING.
As students work, I circulate and ask students questions like:
1) Why did you set this problem up like this?
2) Why did you subtract?
3) Why did you add?
4) What clues did you find to know whether to add/subtract?
Today we worked on solving 2-step word problems. In your math journal, I want you to write about what you learned today and what strategies you used to solve your problems.
This type of reflection gives me a "temperature check" to see what students choose to reflect upon. Students may reflect on what strategies they used or whether they regrouped. Students whose reflections are incoherent oftentimes do not have a clear idea of what the objective was and/or struggled. These reflections are not an exit ticket but rather a chance for students to reflect on what they worked on and for me to gauge their understanding of the material.