Regrouping Readiness Warm-Up

Instructions: Solve the following problems. Show your work on your whiteboard.

1. What is the value of the underlined digit?

   • 35
     
     
     
   • 72
     
     
     

2. Solve these addition problems:

   • 14 + 3 =
     
     
     
   • 20 + 8 =
     
     
     

3. Solve these subtraction problems:

   • 25 - 5 =
     
     
     
   • 38 - 10 =
     
     
     

4. If you have 10 ones, what can you trade them for?
   
   
   
   

Teacher Script: Regrouping Ruckus

Warm-Up (5 minutes)

(Display Warm-Up: Regrouping Readiness)

"Good morning, mathematicians! Today we're going to tackle some exciting two-digit math problems. But first, let's get our brains warmed up with a quick activity."

"On your whiteboards, please solve the problems in your Warm-Up: Regrouping Readiness document. Remember to show your work! I'll be walking around to see your amazing thinking."

(Circulate, observe, and provide individual support. Pay close attention to question 4 about trading 10 ones for a ten.)

"Alright, let's quickly review. For number 4, if you have 10 ones, what can you trade them for? (Pause for responses) That's right, a ten! Keep that in mind, it's going to be super important today."

Introduction to Regrouping (Addition) (8 minutes)

(Display Regrouping Ruckus Slide Deck - Slide 1: "Welcome to Regrouping Ruckus!")

"Welcome to the Regrouping Ruckus! Get ready to make numbers work for us!"

(Display Regrouping Ruckus Slide Deck - Slide 2: "Adding with Two Digits")

"We've been adding two-digit numbers, right? We usually add the ones first, then the tens. Most of the time, it's pretty straightforward."

(Display Regrouping Ruckus Slide Deck - Slide 3: "What is Regrouping?")

"But what happens when we add the ones, and we get a number bigger than 9? Like if we have 7 ones and add 5 more ones? Count it out with your fingers or blocks. How many do you have? (Pause) 12 ones! Can we write '12' in the ones place? No, because each place value can only hold a single digit from 0 to 9."

"This is where regrouping comes in! When we have 10 or more ones, we can bundle 10 of those ones together and trade them for 1 ten. It's like exchanging 10 pennies for a dime!"

(Use base-ten blocks to demonstrate: 7 ones + 5 ones = 12 ones. Physically group 10 ones and replace them with 1 ten stick, leaving 2 ones. Emphasize the exchange.)

"So, 12 ones becomes 1 ten and 2 ones. We write the 2 in the ones place, and we 'carry over' the new ten to the tens place."

(Display Regrouping Ruckus Slide Deck - Slide 4: "Let's Add! (with Regrouping)")

"Let's try an example together: 27 + 15. On your whiteboards, write down 27 + 15 vertically."

"First, let's add the ones column: 7 + 5. What did we just learn? That's 12! We write the 2 in the ones column, and what do we do with the '1' from the 12? (Guide them to say 'carry it over to the tens place'). Yes! We write a small 1 above the tens column."

"Now, let's add the tens column: 2 + 1, plus that new 1 we carried over. So, 2 + 1 + 1 equals...? (Pause) 4! We write 4 in the tens column."

"What's our answer? 42! Great job!"

Introduction to Regrouping (Subtraction) (8 minutes)

(Display Regrouping Ruckus Slide Deck - Slide 5: "Subtracting with Two Digits")

"Now let's think about subtraction. We usually take away the ones first, then the tens. But what if we don't have enough ones to take away?"

(Display Regrouping Ruckus Slide Deck - Slide 6: "What if We Don't Have Enough?")

"Imagine you have 3 cookies, but your friend wants 8. Do you have enough? No! What do you do? You need to find more cookies! In math, we do something similar."

"When we don't have enough ones to subtract, we go to our neighbor, the tens place, and we unbundle a ten. What do you think happens when we unbundle 1 ten? How many ones do we get? (Guide them to say '10 ones'). Exactly! 1 ten becomes 10 ones."

(Use base-ten blocks to demonstrate: Start with 1 ten and 3 ones. Physically take a ten stick and break it into 10 ones, adding them to the existing 3 ones. Show how 1 ten and 3 ones become 0 tens and 13 ones, or 3 tens and 3 ones become 2 tens and 13 ones.)

"So, we take 1 ten from the tens place, and we add 10 ones to our ones place. Now we have plenty of ones to subtract!"

(Display Regrouping Ruckus Slide Deck - Slide 7: "Let's Subtract! (with Regrouping)")

"Let's try this example: 43 - 18. On your whiteboards, write 43 - 18 vertically."

"Look at the ones column: Can we do 3 - 8? No! So, what's our first step? (Guide them to say 'go to the tens place'). Yes! We go to the 4 in the tens place. We take 1 ten from the 4, so the 4 becomes a 3. Now we have 3 tens."

"Where does that ten go? We unbundle it and add 10 ones to our 3 ones. So, 3 ones becomes 13 ones. Write a small 1 next to the 3 in the ones place."

"Now we can subtract the ones: 13 - 8. What's 13 - 8? (Pause) 5! Write 5 in the ones column."

"Next, subtract the tens. We had 4 tens, but we unbundled one, so we now have 3 tens. What's 3 - 1? (Pause) 2! Write 2 in the tens column."

"Our answer is 25! Great work figuring out that tricky problem!"

Practice Quest (7 minutes)

(Display Regrouping Ruckus Slide Deck - Slide 8: "Time to Practice!")

"You've done an awesome job understanding regrouping! Now it's time for your Worksheet: Regrouping Practice Quest. I'm handing out a worksheet with a few practice problems. Work independently on the first few problems, and I'll be around to help if you get stuck."

(Distribute Worksheet: Regrouping Practice Quest. Circulate and provide individualized support. Use the Answer Key: Regrouping Practice Quest to offer immediate, constructive feedback.)

"Remember to think about whether you need to regroup for each problem!"

Cool-Down (2 minutes)

(Display the Cool-Down: Regrouping Review Relay on the projector or quickly write it on the board)

"Alright everyone, time for our final thought. On your whiteboards, please answer the questions on the Cool-Down: Regrouping Review Relay. This will help me see what you learned today."

(Collect whiteboards or observe responses as students leave.)

"Thank you for participating in the Regrouping Ruckus! You all did a fantastic job today!"

Regrouping Practice Quest

Instructions: Solve the following addition and subtraction problems. Remember to regroup when you need to! Show your work.

Part 1: Addition Adventures!

1.    28
   
   + 14
   
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2.    36
   
   + 27
   
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3.    45
   
   + 19
   
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4.    53
   
   + 28
   
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Part 2: Subtraction Challenges!

1.    32
   
   - 17
   
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2.    45
   
   - 26
   
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3.    51
   
   - 29
   
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4.    60
   
   - 34
   
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Regrouping Practice Quest Answer Key

Part 1: Addition Adventures!

1. 28 + 14

   • Step 1: Add the ones. 8 + 4 = 12 ones. We can't write 12 in the ones place!
   • Step 2: Regroup. 12 ones is 1 ten and 2 ones. Write down the 2 in the ones place and carry over the 1 ten to the tens place.
   • Step 3: Add the tens. 2 + 1 (the original tens) + 1 (the carried-over ten) = 4 tens.
   • Answer: 42

2. 36 + 27

   • Step 1: Add the ones. 6 + 7 = 13 ones.
   • Step 2: Regroup. 13 ones is 1 ten and 3 ones. Write down the 3 in the ones place and carry over the 1 ten to the tens place.
   • Step 3: Add the tens. 3 + 2 (the original tens) + 1 (the carried-over ten) = 6 tens.
   • Answer: 63

3. 45 + 19

   • Step 1: Add the ones. 5 + 9 = 14 ones.
   • Step 2: Regroup. 14 ones is 1 ten and 4 ones. Write down the 4 in the ones place and carry over the 1 ten to the tens place.
   • Step 3: Add the tens. 4 + 1 (the original tens) + 1 (the carried-over ten) = 6 tens.
   • Answer: 64

4. 53 + 28

   • Step 1: Add the ones. 3 + 8 = 11 ones.
   • Step 2: Regroup. 11 ones is 1 ten and 1 one. Write down the 1 in the ones place and carry over the 1 ten to the tens place.
   • Step 3: Add the tens. 5 + 2 (the original tens) + 1 (the carried-over ten) = 8 tens.
   • Answer: 81

Part 2: Subtraction Challenges!

1. 32 - 17

   • Step 1: Subtract the ones. Can we do 2 - 7? No, 2 is smaller than 7!
   • Step 2: Regroup (Unbundle). Go to the tens place (3 tens). Take 1 ten from the 3 tens, leaving 2 tens. Unbundle that 1 ten into 10 ones and add them to the 2 ones we already have. Now we have 12 ones.
   • Step 3: Subtract the new ones. 12 - 7 = 5 ones. Write 5 in the ones place.
   • Step 4: Subtract the new tens. We now have 2 tens (because we unbundled one). 2 - 1 = 1 ten. Write 1 in the tens place.
   • Answer: 15

2. 45 - 26

   • Step 1: Subtract the ones. Can we do 5 - 6? No, 5 is smaller than 6!
   • Step 2: Regroup (Unbundle). Go to the tens place (4 tens). Take 1 ten from the 4 tens, leaving 3 tens. Unbundle that 1 ten into 10 ones and add them to the 5 ones we already have. Now we have 15 ones.
   • Step 3: Subtract the new ones. 15 - 6 = 9 ones. Write 9 in the ones place.
   • Step 4: Subtract the new tens. We now have 3 tens. 3 - 2 = 1 ten. Write 1 in the tens place.
   • Answer: 19

3. 51 - 29

   • Step 1: Subtract the ones. Can we do 1 - 9? No, 1 is smaller than 9!
   • Step 2: Regroup (Unbundle). Go to the tens place (5 tens). Take 1 ten from the 5 tens, leaving 4 tens. Unbundle that 1 ten into 10 ones and add them to the 1 one we already have. Now we have 11 ones.
   • Step 3: Subtract the new ones. 11 - 9 = 2 ones. Write 2 in the ones place.
   • Step 4: Subtract the new tens. We now have 4 tens. 4 - 2 = 2 tens. Write 2 in the tens place.
   • Answer: 22

4. 60 - 34

   • Step 1: Subtract the ones. Can we do 0 - 4? No, 0 is smaller than 4!
   • Step 2: Regroup (Unbundle). Go to the tens place (6 tens). Take 1 ten from the 6 tens, leaving 5 tens. Unbundle that 1 ten into 10 ones and add them to the 0 ones we already have. Now we have 10 ones.
   • Step 3: Subtract the new ones. 10 - 4 = 6 ones. Write 6 in the ones place.
   • Step 4: Subtract the new tens. We now have 5 tens. 5 - 3 = 2 tens. Write 2 in the tens place.
   • Answer: 26

Regrouping Review Relay

Instructions: On your whiteboard, quickly answer these questions to show what you learned today!

1. When do you need to regroup in addition? (Hint: Think about the ones place!)
   
   
   
   
   
   
   

2. When do you need to unbundle a ten in subtraction? (Hint: Think about having enough ones!)
   
   
   
   
   
   
   

3. Solve this problem:
   35 + 16 =
   
   
   

4. Solve this problem:
   41 - 15 =