2 Develop the Concept: Interactive 10–15 min Overview Interactive Learning In this activity, children will use place-value blocks to add three-digit numbers. Essential Question How can you model and record adding 2 three-digit numbers? Materials Place-Value Mat B (Teaching Tool 8, 1 per pair), hundreds flats (5 per pair), tens rods (20 per pair), unit cubes (20 per pair) Set the Purpose You know how to add two-digit numbers with and without regrouping. Today you will learn how to add three-digit numbers with and without regrouping. Connect You have learned how to regroup 10 ones as 1 ten when adding two-digit numbers. On the board, write 65 ⫹ 86 in vertical form. What is the sum? [151] Did you have to regroup? Explain. [Yes; I had to regroup 10 ones as 1 ten when I added the ones.] Have children work in pairs. On the board, write 246 ⫹ 371 in vertical form. Work with your partner to find the sum. Use your place-value blocks to help you. What is the sum? Do you have to regroup? Allow time for children to work and to discuss their findings. CVbZTT TTTTTTTTTT Lesson Have children find the missing addend in this problem: 796 ⫹ 912 [116] + & , & ( * (# , * Zgh Zadl# + ' - ) ( , ' . & * & + , + ) , * ' +# & & ( * & ' & ) *# & ) * . )# & ' & ( ;DA9 Write the following addition exercises on the board in vertical form: 146 ⫹ 321, 184 ⫹ 375, 264 ⫹ 123, 277 ⫹ 165, 125 ⫹ 391, and 189 ⫹ 248. Then direct children’s attention to Teaching Tool 8. You will use your place-value chart and models to help you add. Work with your partner to find each sum. Record the answers in Items 1–6 on page 559. [467; 559; 387; 442; 516; 437] After children have completed the page, discuss if and how children regrouped for each item. ) ' + Inc. Small-Group Interaction egdk^YZYW '# & & ( ) Education, Model finding the sum with the class. Model each number with your place-value blocks. What do you add first? [The ones] Do you have to regroup? How do you know? [No; 6 plus 1 is 7, which is less than 1 ten.] Now you can add the tens. Do you have to regroup? How do you know? [Yes; 4 tens plus 7 tens is 11 tens, or 110, which is more than 1 hundred.] How can you regroup 10 tens rods? [You can trade 10 tens rods for one hundreds flat.] Now add the hundreds. How many hundreds are there? [6 hundreds; 2 hundreds plus 3 hundreds plus the regrouped 1 hundred.] What is the sum? [617] © Pearson Model/ Demonstrate TT TTTTTTTTTT TTTTTTTTT B d Y Z ah [ d g 6 Y Y ^c \ l I ] gZ Z " 9 ^\ ^i ] &-"( ^i C j b W Z gh HVbeaZVc &# hl ;DA9 Pose the Problem & ' ) & ) ( . , =dbZ8dccZ =dbZ6Xi^k^i Xi^dc NdjgX]^aYjhZ YeaVXZ n =VkZndjg X]^aYYgVle "kVajZbdYZahid JcYZghiVcY VY aVXZ"kVajZ >i BdYZa WadX`hid Yi]gZZ"Y^\^icjbWZg hXVcWZj bdYZai]Z hZYid]Zael VYY^i^dcd[& h# ]ZcVYY^c *- &)+# \'i]gZZ"Y^\ Ide^X&- ^icjbWZgh# AZhhdc( [^kZ]jcYgZY [^[in"c^cZ **. eTools Place-Value Blocks www.pearsonsuccessnet.com Models for Adding with Three-Digit Numbers 559 28273_559a-562b_PDF.indd 559 6/27/07 1:17:39 PM

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