Возрастная группа: Ye ar 3, Ye ar 4 The Australian Curriculum: ACM N A05 5 NSW Mathematics K-10 Syllabus: M A2-5 N A, M A2-5 N A.

Transcription

1 1 План урока Ad d ing Three Digit Numbers Возрастная группа: Ye ar 3, Ye ar 4 The Australian Curriculum: ACM N A05 5 NSW Mathematics K-10 Syllabus: M A2-5 N A, M A2-5 N A. Victorian Curriculum: VCM N A105, VCM N A13 3 NSW Numeracy Continuum K-10: 3.A4.4 Онлайн ресурсы: B ubbl e Addi t i o n Opening Teacher present s Students play Pract ice Class discussion Closing ЦЕЛИ: E xpe ri e nc e an application of the Commutative Property P rac t i c e adding three digit numbers Learn to compose and decompose three digit numbers De vel o p an understanding of the addition algorithm

2 2 Ope ni ng 4 Display the following problems. Have the students solve them in their notebooks. 1. Add the numbers: a = b = c = 2. Now, do the opposite. Write in e xpa nde d no t a t io n. The first one is done for you. a. 865 = b. 264 = c. 379 = d. 812 = When the students are done working, review the solutions. Say: We re going to use expanded notation to help us add three digit numbers. T e ac he r prese nt s B ubbl e Addi t i o n Addi ng up t o

3 3 Present Matific s episode B ubbl e Addi t i o n - Addi ng up t o 1000 to the class, using the projector. The goal of the episode is to add three digit numbers by first changing into expanded notation and then combining ones with ones, tens with tens, and hundreds with hundreds. Example : The episode has already separated one bubble into its expanded notation. Click on the other original bubble to separate it into separate bubbles. Ask: What have we done by clicking on the bubbles? We have rewritten the adde nds into their expanded notation. Ask: Have we changed the value of the addends by doing this?

4 4 No, the value of the numbers is unchanged. Ask: Have we changed the sum of the numbers by separating the bubbles? No, the sum remains unchanged. Move two bubbles with the same place value together. The episode will ask for their sum. Ask the students for the sum. Click on the enter their answer. within the episode to If the answer is correct, the two bubbles will merge into one with the sum written on it. If the answer is incorrect, the equation will wiggle. Continue moving bubbles with the same place value together and asking the students for their sum. It may be necessary to separate bubbles again, if the sum contains more than one non-zero digit. Once the episode contains one bubble per place value, ask the students for the entire sum. Enter the final answer by clicking on the at the bottom of the screen. If the answer is correct, the episode will proceed to the next problem. If the answer is incorrect, the instructions will wiggle.

5 5 The episode will present a total of six problems. St ude nt s pl ay B ubbl e Addi t i o n Addi ng up t o Have the students play B ubbl e Addi t i o n - Addi ng up t o 1000 on their personal devices. Circulate, answering questions as necessary. P rac t i c e 10 Have the students work on the following worksheets: Addi t i o n - H undreds and Addi t i o n - Up t o 1000 on their personal devices. Circulate, answering questions as necessary. Cl ass di sc ussi o n 10 Say: Let s suppose the episode presented us with two bubbles: one that read 423 and one that read 568. What bubbles would we split 423 into? What bubbles would we split 568 into? We would split 423 into a 400 bubble, a 20 bubble, and a 3 bubble. We would split 568 into a 500 bubble, a 60 bubble, and an 8 bubble. Write on the board: = ( ) + ( ) Ask: How should we now combine the bubbles? Let s combine the 400 with the 500, the 20 with the 60, and the 3

6 6 with the 8. Ask: What are we doing when we add in this way? We are combining ones with ones, tens with tens, and hundreds with hundreds. Add to the writing on the board, so that now it reads: = ( ) + ( ) = ( ) + ( ) + (3 + 8) Ask: Why can we rearrange the addends? An addition problem is not changed by rearranging the order of the addends. Say: So adding those numbers, we now have 900, 80, and 11. Let s split the 11 into two bubbles. How should we do that? We can change 11 into 10 and 1. Add to the writing on the board, so that now it reads: = ( ) + ( ) = ( ) + ( ) + (3 + 8) = (900) + (80) + (11) = (900) + (80) + (10 + 1) Ask: Now what should we do? We can add the 80 and the 10 to get 90. Add to the writing on the board, so that now it reads: = ( ) + ( ) = ( ) + ( ) + (3 + 8) = (900) + (80) + (11) = (900) + (80) + (10 + 1)

7 7 = (900) + ( ) + (1) = (900) + (90) + (1) Say: We can easily see that the sum is 991. Often, we see addition written this way: Ask: What does that little one at the top of the problem mean? Where does it come from? Connect the 1 to the work we ve been doing with the bubbles. The one is from the 3 and the 8. They added to become 11. When we were using the bubbles, we split 11 into 10 and 1. Here, we are also splitting the 11 into 10 and 1. The 1 we write in our answer. The 10 we write as just a 1, but we put that 1 in the tens place to represent the fact that it is standing for 10.

8 8 Cl o si ng 3 Ask each student to write down the steps that they would take using the episode s method of adding 456 and 382. Responses should resemble: = ( ) + ( ) 2. = ( ) + ( ) + (6 + 2) 3. = (700) + (130) + (8) 4. = (700) + ( ) + (8) 5. = ( ) + (30) + (8) 6. = = 838 When the students are done writing, review their responses. Discuss any questions the students may have.