Solving addition or subtraction problems involving mass - math grade 2 - lesson 54

Yesterday we solved addition story problems involving mass. Today we are going to continue practicing this skill by solving addition and subtraction problems involving grams and kilograms. Before we start, I am going to give you 1 minute to tell me everything you know about grams and kilograms.

Note to the Teacher: In this lesson, students solve addition and subtraction story problems involving mass. Students strengthen and apply their skills in these mathematical concepts by creating their own mass story problems. Students swap story problems with a partner to solve one another’s problems. If you have g/kg scales or two-pan balances available, a great extension or substitute lesson would be to put students in small groups with sets of 5 or 6 items of different masses. Have the students choose 2 items and either measure or compare their masses. (See Chapter Preparation for the Teacher for detailed instruction on creating a two-pan balance.)

STUDENTS DO: Share with their Shoulder Partner everything they remember about grams and kilograms. Take turns with their partner.

TEACHER DO: Place 5 bags of rice in a box at the front of the room with a 1 kilogram label on each bag and a 5 kilogram label on the box.

TEACHER SAY: Great job. We have learned so much about measuring mass. I have the same 5 bags of rice that I had yesterday. Remember, each bag has a mass of 1 kilogram. Work with your Shoulder Partner to create a story problem involving these 5 bags of rice. It can be an addition problem or a subtraction problem. I will give you 2 minutes.

STUDENTS DO: Work with their Shoulder Partner to create a story problem about the 5 bags of rice.

TEACHER DO: As students work, walk around and listen to their conversations. Offer help as needed. After about 2 minutes, use an Attention Getting Signal to refocus students.

TEACHER SAY: Raise your hand if you and your Shoulder Partner would like to share your story problem. I will ask three of you to share your story problems.

STUDENTS DO: Raise hand to volunteer. Selected students share the story problems they created. All students work to solve their friends’ story problems.

TEACHER SAY: Now you will work with partners to solve some story problems in your student book. Open your student book to page Lesson 54: Apply.

STUDENTS DO: Open student book to page Lesson 54: Apply.

TEACHER DO: Select partners for the students. Try to include at least one strong reader in each pair. If necessary, have students work in groups of three.

TEACHER SAY: Similar to yesterday, you will see four story problems. Be sure to read each story problem carefully. Think carefully about each problem so you know whether you have to add or subtract. After the story problems, there are two empty boxes numbered 5 and 6. This is where you will create your own story problems with your partners. The problems can be addition or subtraction problems. They can be about grams or kilograms. They just have to be story problem involving mass. Draw pictures to go with your problems. What questions do you have?

STUDENTS DO: Ask clarifying questions, if necessary. Work with partners to solve the story problems and then create two story problems related to mass.

TEACHER SAY: Make sure BOTH of you (or everyone in the group if students are working with two partners) write and draw the story problems in your student books.

TEACHER DO: Students who finish early can make a list of objects in the classroom and estimate their weights in grams or kilograms. When all students are finished, use an Attention Getting Signal to refocus students. Select partners to share their solutions to problems 1 through 4 with the class.

STUDENTS DO: Selected students share their answers and explain how they solved the problem.

TEACHER SAY: Wonderful. I like how you work together to solve problems and help each other.