Teacher Script: Subtracting Superstars

Warm-Up: Ready, Set, Subtract! (5 minutes)

"Good morning, future math superstars! Let's get our brains warmed up for some subtraction. I have a quick challenge for you. On your own paper, I want you to quickly solve these two problems:

1. 45 - 23 =
2. 78 - 39 =

Take about two minutes. Remember what we know about place value and basic subtraction. Go!"

(Allow students to work. Circulate and observe their strategies, especially for the second problem.)

"Alright, pencils down! Let's quickly share. For 45 - 23, who has the answer? [Call on a student]. Yes, 22. Great! And for 78 - 39? [Call on a student]. Interesting! Some of you might have noticed something different about that second problem. Hold that thought, we're going to dive deeper into those kinds of problems today!"

Introduction to 3-Digit Subtraction with Regrouping (10 minutes)

(Transition to Subtracting Superstars! Slide Deck - Slide 1)

"Today, we're going to become subtraction superstars! We'll learn how to subtract big numbers and even use a special trick called 'regrouping'."

(Advance to Slide 2)

"What exactly is 3-digit subtraction? Well, it's just subtracting numbers that have hundreds, tens, and ones. Think about it: you see these kinds of numbers all the time! Who can give me an example of when you might subtract big numbers in real life? [Wait for student responses, guide them if needed].

Great examples! Maybe when you're helping your parents figure out how much money they have left after shopping, or if you're planning a long road trip and need to know how many more miles you have to go. It's a super useful skill!"

(Advance to Slide 3)

"Now, sometimes, we run into a little problem when we're subtracting. Imagine you have 2 cookies, and your friend wants 8. Do you have enough to give them? No! That's exactly what happens in math sometimes. We don't have enough to subtract in one place value column. But don't worry, we have a superpower! It's called regrouping, and it helps us 'borrow' from the next column over to make enough. It's like going to your neighbor and asking for a cup of sugar when you run out!"

(Advance to Slide 4)

"Let's quickly review a simple 3-digit subtraction problem where we don't need our superpower. Look at 345 - 123. Remember, we always start with the column on the far right, the ones place. What's 5 - 3? [Wait for response]. Yes, 2. Now the tens place, 4 - 2? [Wait]. Good, 2. And finally, the hundreds place, 3 - 1? [Wait]. Excellent, 2. So, 345 - 123 equals 222."

(Advance to Slide 5)

"Okay, now let's use our superpower! Look at 452 - 138. Again, we start at the ones place. Can we do 2 - 8? [Wait for response]. No, we can't! We don't have enough ones. So, we need to regroup! We're going to go to our neighbor, the tens place. The 5 in the tens place is going to lend us one of its tens. So, the 5 tens becomes 4 tens. And that 1 ten we borrowed? It's really 10 ones, so we add it to our 2 ones, making it 12 ones.

Now, can we do 12 - 8? [Wait]. Yes! It's 4. Write that in the ones place.

Next, the tens place. Remember, we now have 4 tens. What's 4 - 3? [Wait]. That's 1. Write that in the tens place.

Finally, the hundreds place. What's 4 - 1? [Wait]. Yes, 3. Write that in the hundreds place.

So, 452 - 138 is 314! Great job, everyone!"

(Advance to Slide 6)

"Let's try another one. This time, we might need to regroup in a different spot. Look at 624 - 281.

Start with the ones. What's 4 - 1? [Wait]. Good, 3. Write it down.

Now, the tens place. Can we do 2 - 8? [Wait]. No, we can't! So, what do we do? [Wait for student to suggest regrouping]. Exactly! We go to our hundreds neighbor. The 6 hundreds becomes 5 hundreds. And that 1 hundred we borrowed? It's 10 tens, so we add it to our 2 tens, making it 12 tens.

Now, what's 12 - 8? [Wait]. That's right, 4. Write that in the tens place.

Last but not least, the hundreds place. What's 5 - 2? [Wait]. You got it, 3. Write that in the hundreds place.

Our answer is 343! You're getting the hang of this superpower!"

(Advance to Slide 7)

"Whoa! Look at this one: 531 - 276. This problem might require us to use our regrouping superpower more than once! Don't be scared, we can do it!

Let's start at the ones place: Can we do 1 - 6? [Wait]. No! So, what's our first step? [Wait for student to say regroup from tens]. Perfect! The 3 tens become 2 tens, and our 1 one becomes 11 ones. Now, 11 - 6 is? [Wait]. 5! Write it down.

Now to the tens place: We have 2 tens, and we need to subtract 7 tens. Can we do 2 - 7? [Wait]. Nope! What's our next regrouping step? [Wait for student to say regroup from hundreds]. Awesome! The 5 hundreds becomes 4 hundreds, and our 2 tens become 12 tens. Now, 12 - 7 is? [Wait]. 5! Write it down.

Finally, the hundreds place: We have 4 hundreds, and we subtract 2 hundreds. 4 - 2 is? [Wait]. 2! Write it down.

So, 531 - 276 equals 255! That was some excellent double regrouping!"

(Advance to Slide 8)

"Here are some tips for success that will help you when you're working on these problems. Always start with the ones place. If you don't have enough, regroup from the next place value. Show your work! Crossing out numbers helps you keep track. And a super important tip: you can always check your answer using addition! We'll talk more about that later.

Guided Practice (5 minutes)

"Let's do a couple more together as a class. I want you to work with me. Get out your whiteboards or a piece of scratch paper. I'll write the problem on the board, and we'll go through it step by step, with you telling me what to do.

(Write 734 - 219 on the board)

"Okay, for 734 - 219, where do we start? [Wait for 'ones place']. Good. Can we do 4 - 9? [Wait for 'no']. So what do we do? [Wait for 'regroup from tens']. Excellent! What does the 3 become? [2]. What does the 4 become? [14]. Now, 14 - 9 is? [5]. Write it down!

Next, the tens place. We have 2 tens. Can we do 2 - 1? [Yes]. What's 2 - 1? [1]. Write it down!

Finally, the hundreds place. What's 7 - 2? [5]. Write it down!

So, 734 - 219 is 515! Fantastic teamwork!"

(Repeat with another problem like 805 - 342, emphasizing the zero in the tens place and regrouping across zero if time allows, or focus on another double regrouping example if the class needs more support.)

Independent Practice: Subtraction Practice Worksheet (8 minutes)

(Advance to Slide 9)

"You've done an amazing job with our guided practice! Now it's your turn to be a true Subtraction Superstar on your own. I'm going to hand out this Subtraction Practice Worksheet. You'll find a few 3-digit subtraction problems on it. Remember all the tips we just talked about: start with the ones, regroup when you need to, and show your work!

(Distribute the worksheets. Circulate around the room, offering individual support and encouragement.)

Cool-Down: Subtraction Reflection (2 minutes)

(Advance to Slide 10)

"Pencils down, everyone. You've worked hard today! For our cool-down, I want you to take out your Cool-Down: Subtraction Reflection sheet. Take about a minute or two to answer the questions honestly. This helps me understand what you learned and what we might need to review.

(Collect cool-down sheets as students finish.)

"You've learned an amazing math superpower today! Keep practicing, and you'll master 3-digit subtraction in no time! Great job, Subtraction Superstars!"

Warm-Up: Ready, Set, Subtract!

Instructions: Solve the following subtraction problems. Show your work!

1. 45 - 23 =
   
   
   
   

2. 78 - 39 =
   
   
   
   

Subtraction Practice Worksheet

Instructions: Solve each 3-digit subtraction problem. Remember to show your regrouping! If you need more space, use the back of this sheet.

1. 573 - 241 =
   
   
   
   
   
   
   

2. 680 - 357 =
   
   
   
   
   
   
   

3. 425 - 183 =
   
   
   
   
   
   
   

4. 700 - 345 =
   
   
   
   
   
   
   

5. 912 - 568 =
   
   
   
   
   
   
   

Subtraction Practice Answer Key

Here are the step-by-step solutions for the Subtraction Practice Worksheet:

1. 573 - 241 =

• Ones Place: 3 - 1 = 2
• Tens Place: 7 - 4 = 3
• Hundreds Place: 5 - 2 = 3
• Answer: 332

2. 680 - 357 =

• Ones Place: We can't do 0 - 7, so we regroup from the tens place.
  • The 8 tens becomes 7 tens.
  • The 0 ones becomes 10 ones.
  • Now, 10 - 7 = 3
• Tens Place: 7 - 5 = 2
• Hundreds Place: 6 - 3 = 3
• Answer: 323

3. 425 - 183 =

• Ones Place: 5 - 3 = 2
• Tens Place: We can't do 2 - 8, so we regroup from the hundreds place.
  • The 4 hundreds becomes 3 hundreds.
  • The 2 tens becomes 12 tens.
  • Now, 12 - 8 = 4
• Hundreds Place: 3 - 1 = 2
• Answer: 242

4. 700 - 345 =

• Ones Place: We can't do 0 - 5. We look to the tens, but it's also 0. So, we regroup from the hundreds place.
  • The 7 hundreds becomes 6 hundreds.
  • The 0 tens becomes 10 tens.
  • Now, we regroup from the 10 tens for the ones place.
    • The 10 tens becomes 9 tens.
    • The 0 ones becomes 10 ones.
  • Now, 10 - 5 = 5
• Tens Place: (Remember it's now 9 tens) 9 - 4 = 5
• Hundreds Place: (Remember it's now 6 hundreds) 6 - 3 = 3
• Answer: 355

5. 912 - 568 =

• Ones Place: We can't do 2 - 8, so we regroup from the tens place.
  • The 1 ten becomes 0 tens.
  • The 2 ones becomes 12 ones.
  • Now, 12 - 8 = 4
• Tens Place: We can't do 0 - 6, so we regroup from the hundreds place.
  • The 9 hundreds becomes 8 hundreds.
  • The 0 tens becomes 10 tens.
  • Now, 10 - 6 = 4
• Hundreds Place: (Remember it's now 8 hundreds) 8 - 5 = 3
• Answer: 344

Cool-Down: Subtraction Reflection

Instructions: Please answer the following questions to help me understand your learning today.

1. What was one new thing you learned about 3-digit subtraction today?
   
   
   
   

2. What is one thing that still confuses you or that you would like more practice with?
   
   
   
   

3. Why is it important to learn how to subtract 3-digit numbers?