1. Module 5 Lesson 13

2. Objective Relate manipulative representations to the subtraction algorithm, and use addition to explain why the subtraction method works.

3. Application Problem A fruit seller buys a carton of 90 apples. Finding that 18 of them are rotten, he throws them away. He sells 22 of the ones that are left on Monday. How many apples does he have left to sell?

4. Fluency Practice When I say 9 + 4, you write 10 + 3. Ready? 9 + 4. Tell me the number sentence with the answer. Write the related addition sentence starting with 9 + 4. 19 + 49 + 619 + 68 + 318 + 3 8 + 517 + 67 + 417 + 4 9 + 5 19 + 58 + 617 + 88 + 718 + 6

5. Fluency Practice Let’s find missing part to make the next hundred. What is the next hundred? If I say 170, you say the missing number needed to make 200. Ready? 170. Tell me the addition sentence. 170 224214196194940 740720620580380 370270260 160 190

6. Fluency Practice What is 2 tens less than 130? Give the subtraction number sentence. What is 2 hundreds less than 350? Give the subtraction number sentence. 6 tens less than 150 7 tens less than 250 6 tens less than 3404 hundreds less than 880 3 hundreds less than 550

7. Concept Development Problem 1: 244 – 121 Read this problem with me. How would you complete this number bond? Talk to a partner and use part–whole language Great! What do we need to show on our place value charts? Talk to your neighbor. Count in unit form as I place the chips. 244 121 100s10s1s

8. Concept Development Problem 1 Continued: 244 – 121 Today, as we solve subtraction problems, we are going to record our work vertically. Remember our magnifying glasses! Let’s draw an imaginary magnifying glass around 244, since that is the whole. Like a detective, look carefully at each place to see if we have enough units to subtract moving from the smallest unit to the largest. Are we ready to subtract in the ones, tens, and hundreds? Go for it!

9. Concept Development Problem 1 Continued: 244 – 121 What is 244 – 121? Now, using our number bond, I bet it’s easy for someone to come up with a related addition problem to check our answer. What problem should we write? Solve this problem on your boards and turn them over when you have the answer. What is the sum? It worked! 244 123 121

10. Concept Development Problem 2: 244 – 125 Let’s try another problem together. This time I want you to record your work as I do mine. What should we do first? True! For this problem, let’s solve using the algorithm. Show me the whole using your number disks. Draw the magnifying glass with enough space to write renaming. Okay, I’m looking closely. Where do we start? Can we subtract 5 ones from 4 ones? 244 - 125 14 3 What should we do? Okay, go ahead and show that change using your disks. Whatever we do to our number disks, we must also do on the vertical subtraction. How should we record unbundling a ten? Now, how many tens and ones do we have on our charts? Look at each column closely. Tell me, are we ready to subtract? Then let’s subtract! What is the answer to 244 – 125? Check your answer with addition. Write a complete number bond. Does it work?

11. Concept Development Problem 3: 312 – 186 Let’s try another problem together. I’m going to follow what you do. What is different about this problem? Let’s see if we need to unbundle. Do we have enough ones? Do we have enough tens? Let’s unbundle to get ready to subtract. What should we do? Are we ready to subtract in the ones place? How many ones do we have now? How many tens? Are we ready to subtract in the tens place? How many tens do we have now? How many hundreds? Are we ready to subtract 186 from 312?