Add and subtract money without regrouping - math grade 2 - lesson 66

Learn (40 minutes)

Directions

1. TEACHER SAY: Let’s review a little bit about what we have learned by playing a game called Show What You Know. First, stand up and find a partner using Hands Up, Pair Up.

STUDENTS DO: Find a partner using Hands Up, Pair Up.

TEACHER SAY: I am going to ask a question. Talk to your partner about the answer. When you and your partner agree on an answer, wave your hands in the air. The first question is: What do we call our currency?

STUDENTS DO: Take turns sharing what they know with partners. Wave their hands when they agree on the answer. Selected partners share their answer with the class.

TEACHER DO: Continue the game with the questions below.

• What is the largest banknote we have used in class?
• What is the smallest banknote we have used in class?
• Why do we need to know how to add and subtract money?
• What questions do you still have about money? Talk to your partner.
• Select a few students to share their questions. See if any students are able to answer their friends’ questions.

2. TEACHER SAY: Great job reviewing. Please open your Mathematics Student Book to page Lesson 66: Apply.

STUDENTS DO: Open student books to Lesson 66: Apply.

TEACHER SAY: Today we are going to use money in a different way. We are going to solve story problems using money. Remember, when we have a story problem, the first thing we have to do is figure out what question we are trying to answer. Then we have to figure out what information we have and whether we should add or subtract to find that answer. Let’s try one together. Point to the empty box at the top of the page.

STUDENTS DO: Point to the empty box at the top of the page.

TEACHER SAY: I am going to give you a story problem. Record your work in the empty box. When you are finished, compare your answer with your Shoulder Partner’s. Give me a Thumbs Up when you are finished.

TEACHER DO: Read the story problem aloud at least two times: My grandmother gave me 55 LE for my birthday. I bought a stuffed bear for 34 LE. How many pounds do I have left?

STUDENTS DO: Solve the problem, compare answers with their Shoulder Partner, and give a Thumbs Up when finished.

TEACHER DO: Observe students as they work. Take note of students who do not choose the correct operations to solve the problems.

Note to the Teacher: To extend students’ learning using computational thinking skills, adjust the procedure of this lesson as follows: Share the correct answer and ask students to identify and correct their errors. Identifying and fixing mistakes is an important computational thinking skill and students will benefit from the experience of reviewing and reflecting on their own work.

STUDENTS DO: Selected students share their work and thinking with the class.

TEACHER DO: Write the problem on the board: 55 LE – 34 LE =

TEACHER SAY: Let’s think about this problem another way—by using place value. Both of these numbers are 2-digit numbers with digits in the Tens and Ones places. When we subtract, we start with the Ones place. I see 5 Ones minus 4 Ones. What is 5 – 4? Show me on your fingers.

STUDENTS DO: Show 1 on their fingers.

TEACHER SAY: In the Tens place, I see a 5 and a 3. What is 5 Tens minus 3 Tens? Show me on your fingers.

STUDENTS DO: Show 2 on their fingers.

TEACHER DO: Add the answer to the equation on the board.

TEACHER SAY: Notice that I wrote LE after 21. Why is it important for us to always write LE after our answer when we are solving a problem with money?

STUDENTS DO: Raise hand to answer. Selected students share their thinking.

3. TEACHER SAY: Correct. The problem asked how many pounds I have left. My answer is not 21. My answer is that I have 21 LE left. Are you ready to try some on your own? You will solve the story problems in your student book. Remember, you have to think about what the question is asking, then figure out whether you have to add or subtract. Pay close attention to the words in the story.

STUDENTS DO: Work independently to solve each money story problem using addition or subtraction.

TEACHER DO: Circulate around the room, offering help to students who need it. Ask some students to explain their thinking and problem-solving strategies. Use this time to take note of which students are struggling with the math concepts. When students finish, go over the answers together or have students check their work with their Shoulder Partners as time allows.

STUDENTS DO: Check their answers, making corrections if necessary.