subtracting money with regrouping - math grade 2 - lesson 69

Math4u grade 2 second term

ماث فور يو جريد 2 

math grade 2 second term

Mathematics Teacher`s Guide primary 2

Math primary 2 second term lesson 69

Note to the Teacher: In today’s lesson, students continue to connect their understanding of place value to the 1, 10, and 100 LE notes. This lesson focuses on subtracting with regrouping. The process of students working with the teacher, working with a partner, and showing their work is repeated. Note that students are working with their Shoulder Partner in this lesson. However, if they do not have enough banknotes to solve the subtraction problems, have them work in teams of three instead.

1. TEACHER DO: Display the place value/money mat on the board. Have your large banknotes nearby.

TEACHER SAY: Open your Mathematics Student Book to page Lesson 69: Apply. Take out your 1, 10, and 100 LE banknotes.

STUDENTS DO: Open student book to page Lesson 69: Apply. Take out 1, 10, and 100 LE banknotes.

TEACHER SAY: Like yesterday, there is a place value/money mat on the page. I also have one on the board. Let’s begin. Work with your Shoulder Partner to show 325 LE on your mat.

STUDENTS DO: Work with Shoulder Partner to show 325 LE on their mat.

TEACHER DO: Show 325 LE on your large mat.

TEACHER SAY: Let’s subtract 119 LE.

TEACHER DO: Write 325 LE – 119 LE = _____ on the board.

TEACHER SAY: Where do we always begin when we add or subtract?

STUDENTS DO: Call out: Ones place.

TEACHER SAY: Correct. Let’s look at the Ones column. How many Ones are there in 325 LE? Call out if you know.

STUDENTS DO: Call out: 5.

TEACHER SAY: How many Ones are there in 119 LE?

STUDENTS DO: Call out: 9.

TEACHER SAY: We have 5 Ones and have to subtract 9. Can we do that? Hold up 5 fingers.

STUDENTS DO: Hold up 5 fingers.

TEACHER SAY: Now, subtract 9 fingers.

STUDENTS DO: Try to subtract 9 fingers. Students should recognize that they cannot.

TEACHER SAY: We do not have enough Ones to subtract 9. When that happens, we must decompose a Ten and bring it over to the Ones place. Watch.

TEACHER DO: Take one of the 10 LE notes from the Tens column on your mat. Hold it up so all students can see it.

TEACHER SAY: I have one of the 10 LE notes from the Tens column. How many 1 LE notes is this worth? Call out if you know.

STUDENTS DO: Call out: 10.

TEACHER SAY: Yes, one 10 LE note is worth ten 1 LE notes. I take my 10 LE note and I decompose it into ten 1 LE notes. Now that they are 1 LE notes, they can go in the Ones column. Now you do it. Take one of your 10 LE notes and regroup it into ten 1 LE notes. Place them in the Ones column with the rest of the 1 LE notes.

STUDENTS DO: Regroup one 10 LE note into ten 1 LE notes. Place them in the Ones column.

TEACHER SAY: Now how many 1 LE notes do we have now?

STUDENTS DO: Add notes. Call out: 15.

TEACHER SAY: We have 15. Can we subtract 9 now?

STUDENTS DO: Call out: yes.

TEACHER SAY: Yes. Subtract 9 and raise your hand when you and your partner have an answer.

STUDENTS DO: Subtract 9 from 15. Raise hand when ready. Selected students share their answer and demonstrate their work at the board.

TEACHER SAY: Great work. Now how many 10 LE notes do we have in the Tens column?

STUDENTS DO: Call out: 1.

TEACHER SAY: Yes. We started with two 10 LE notes, but we regrouped one of them and moved it to the Ones place so we could subtract. Now we have one 10 LE note left. Look at our problem. How many Tens do we need to subtract?

STUDENTS DO: Look at the problem. Call out: 1.

TEACHER SAY: Yes. Take one 10 LE note away from your Tens column. What is 1 minus 1?

STUDENTS DO: Call out: 0.

TEACHER SAY: Let’s look at the Hundreds column. How many 100 LE notes do we have?

STUDENTS DO: Call out: 3.

TEACHER SAY: Yes. Look at our problem. How many Hundreds do we need to subtract?

STUDENTS DO: Look at the problem. Call out: 1.

TEACHER SAY: Subtract one of the 100 LE notes from your Hundreds column. Raise your hand when you have an answer.

STUDENTS DO: Subtract one 100 LE note. Raise hand when finished. Selected students share their answers and demonstrate their work at the board.

TEACHER DO: Write the answer to the equation on the board: 325 LE – 119 LE = 206.

TEACHER SAY: Great work. Let’s try another one together.

TEACHER DO: In the time left in the Learn segment, repeat the procedure with additional subtraction problems with one instance of regrouping, such as 468 LE – 293 LE. Help students understand that regrouping a 100 LE note into ten 10 LE notes is the same process they followed in the first problem. Have students share their answers, explain their thinking, and demonstrate their work whenever possible.

STUDENTS DO: Work with their Shoulder Partner to solve subtraction problems with regrouping. Selected students share their answers, explain their thinking, and demonstrate their work at the board.

TEACHER SAY: That was a lot of hard work. You are learning so much and I love hearing your thinking. Please keep your student book out and put away your banknotes.

Note to the Teacher: Today students used money and a place value/money mat to strengthen and apply their understanding of place value, subtraction, and regrouping. For Reflect, they are asked to think about the process of regrouping and write about it.

1. TEACHER SAY: Turn in your student book to page Lesson 69: Math Journal.

STUDENTS DO: Turn in the student book to page Lesson 69: Math Journal.

TEACHER SAY: Today, we practiced subtracting with regrouping. In our last math lesson, we practiced adding with regrouping. Think for a moment about the work you did today and yesterday. How is regrouping to add like regrouping to subtract? How is it different? After you have thought about your answer, write about or draw your thinking in your student book on the Math Journal page.

STUDENTS DO: Reflect and then record their thinking in their student book.

TEACHER DO: As students are working, walk around and read some of their entries. Ask some students to explain or elaborate on their thinking. After about three minutes, use an Attention Getting Signal.

TEACHER SAY: I enjoyed reading your journal entries. It helps me understand how you think about mathematics. Please give yourselves a pat on the back and put away your student book for today.

STUDENTS DO: Pat themselves on the back and put away student book.