Decimal Warm Up!

Instructions: Take a few minutes to answer the questions below. Think about what you already know about decimals!

1. Where have you seen decimals outside of school? List at least two places.
   
   
   
   
   
   
   
   
   
   
   
   

2. What do you think the

Decimal Operations Worksheet

Instructions: Solve each addition and subtraction problem. Remember to line up your decimal points!

1. 4.75 + 2.13
   
   
   
   
   
   
   

2. 9.8 - 3.4
   
   
   
   
   
   
   

3. 12.05 + 6.3
   
   
   
   
   
   
   

4. 7.5 - 4.25
   
   
   
   
   
   
   

5. 0.9 + 1.15
   
   
   
   
   
   
   

6. 15.2 - 8.75
   
   
   
   
   
   
   

7. A plant grew 3.8 cm in one week and 2.65 cm the next week. How much did it grow in total over the two weeks?
   
   
   
   
   
   
   
   
   
   
   
   

8. Mark had $20.00. He bought a book for $7.25. How much money does he have left?
   
   
   
   
   
   
   
   
   
   
   
   

Decimal Operations Answer Key

Instructions: Review the solutions and steps for each problem.

1. 4.75 + 2.13

     4.75
   + 2.13
   ------
     6.88
   

   Thought Process: Line up the decimal points. Add the hundredths (5+3=8), then the tenths (7+1=8), then the ones (4+2=6). Bring down the decimal point.

2. 9.8 - 3.4

     9.8
   - 3.4
   -----
     6.4
   

   Thought Process: Line up the decimal points. Subtract the tenths (8-4=4), then the ones (9-3=6). Bring down the decimal point.

3. 12.05 + 6.3

     12.05
   +  6.30  (add a zero)
   -------
     18.35
   

   Thought Process: Line up the decimal points. Add a zero to 6.3 to make it 6.30. Add the hundredths (5+0=5), then the tenths (0+3=3), then the ones (2+6=8), then the tens (1+0=1). Bring down the decimal point.

4. 7.5 - 4.25

     7.50  (add a zero)
   - 4.25
   ------
     3.25
   

   Thought Process: Line up the decimal points. Add a zero to 7.5 to make it 7.50. Subtract the hundredths (0-5, need to borrow, 10-5=5). Subtract the tenths (4-2=2). Subtract the ones (7-4=3). Bring down the decimal point.

5. 0.9 + 1.15

     0.90  (add a zero)
   + 1.15
   ------
     2.05
   

   Thought Process: Line up the decimal points. Add a zero to 0.9 to make it 0.90. Add the hundredths (0+5=5), then the tenths (9+1=10, write 0 carry 1), then the ones (0+1+1=2). Bring down the decimal point.

6. 15.2 - 8.75

     15.20  (add a zero)
   -  8.75
   --------
      6.45
   

   Thought Process: Line up the decimal points. Add a zero to 15.2 to make it 15.20. Subtract the hundredths (0-5, need to borrow, 10-5=5). Subtract the tenths (1-7, need to borrow, 11-7=4). Subtract the ones (4-8, need to borrow, 14-8=6). Bring down the decimal point.

7. A plant grew 3.8 cm in one week and 2.65 cm the next week. How much did it grow in total over the two weeks?

     3.80
   + 2.65
   ------
     6.45 cm
   

   Thought Process: This is an addition problem. Line up the decimal points and add a zero to 3.8 to make it 3.80. Add the hundredths (0+5=5), then the tenths (8+6=14, write 4 carry 1), then the ones (3+2+1=6). Bring down the decimal point.

8. Mark had $20.00. He bought a book for $7.25. How much money does he have left?

     20.00
   -  7.25
   --------
     12.75
   

   Thought Process: This is a subtraction problem. Line up the decimal points. Subtract the hundredths (0-5, need to borrow, 10-5=5). Subtract the tenths (9-2=7). Subtract the ones (9-7=2). Subtract the tens (1-0=1). Bring down the decimal point.

Teacher Script: Decimal Dash

Warm-Up: Decimal Brainstorm (5 minutes)

(Teacher displays Decimal Warm Up on screen)

"Good morning/afternoon class! Let's kick off our Decimal Dash with a quick warm-up. Take about 3-4 minutes to answer the questions on your Decimal Warm Up sheet. Think about where you see decimals in everyday life and what you already know about them."

(After 3-4 minutes)

"Alright, let's hear some of your thoughts! Who can share one place they've seen decimals outside of school?"
(Call on a few students. Prompt for examples like money, sports scores, measurements, nutrition labels.)

"Excellent examples! Now, for the second question, what do you think the decimal point actually does? What's its job?"
(Guide students to understand it separates whole numbers from parts of a whole.)

"Fantastic! It tells us we're moving from whole units to fractions or parts of a unit. Great thinking, everyone!"

Introduction: What's the Point? (5 minutes)

(Transition to Decimal Dash Slide Deck - Slide 1)

"Welcome to the Decimal Dash! Today, we're going to become experts at adding and subtracting decimals. This is a super important skill because decimals pop up everywhere, from figuring out how much change you get at the store to understanding your favorite athlete's stats."

(Advance to Decimal Dash Slide Deck - Slide 2)

"As you can see, decimals are all about showing parts of a whole. Can anyone give me another example of where we might use decimals? Perhaps with baking or building?"
(Encourage a few more student examples.)

"Perfect! Now, let's learn the golden rule for working with these important numbers."

Guided Practice: Let's Dash Together! (10 minutes)

(Advance to Decimal Dash Slide Deck - Slide 3)

"Alright racers, when we add decimals, there's one rule that is more important than any other: we ALWAYS have to line up our decimal points! Think of it like all the cars lining up perfectly at the starting line of a race. If they're not lined up, it'll be a messy start!

Take a look at this example: 2.35 + 1.62. Notice how the decimal points are perfectly stacked? That's what we want!"

(Advance to Decimal Dash Slide Deck - Slide 4)

"Now, once those decimal points are lined up, you just add like you normally would with whole numbers. And don't forget to bring that decimal point straight down into your answer. So, 2.35 + 1.62 gives us 3.97. Easy, right?"

(Advance to Decimal Dash Slide Deck - Slide 5)

"The amazing thing is, the same exact rule applies when we subtract decimals! You still have to line up those decimal points. If you can line them up for adding, you can line them up for subtracting. Here's an example: 5.75 - 2.50."

(Advance to Decimal Dash Slide Deck - Slide 6)

"Just like with addition, once the decimal points are aligned, you subtract as usual. 5.75 minus 2.50 gives us 3.25. Now, here's a pro tip: sometimes numbers might not have the same number of digits after the decimal. If you have 3.5 and need to subtract something with hundredths, just add a zero to 3.5 to make it 3.50. It doesn't change the number, but it helps keep everything organized!"

(Advance to Decimal Dash Slide Deck - Slide 7)

"Okay, it's your turn to practice a bit! On your whiteboards or scratch paper, try this problem: Sarah ran 4.25 miles on Monday and 3.5 miles on Tuesday. How many miles did she run in total? Remember our golden rule!"
(Give students 1-2 minutes to work. Circulate and provide support.)

(Advance to Decimal Dash Slide Deck - Slide 8)

"Who got 7.75 miles? Fantastic! Notice how we added a zero to 3.5 to make it 3.50 so everything lined up perfectly. Excellent work, everyone."

Independent Practice: Your Turn to Dash! (7 minutes)

(Distribute Decimal Operations Worksheet)

"Now it's time for your independent practice! I'm handing out the Decimal Operations Worksheet. You'll have about 7 minutes to work through these problems on your own. Remember all the strategies we just discussed, especially lining up those decimal points. I'll be walking around to answer any questions you might have."

(Circulate and provide individual assistance. Remind students of the time.)

Wrap-Up: Quick Check (3 minutes)

"Alright everyone, pencils down for a moment. Let's quickly review one or two problems from the worksheet. Can someone share their answer and how they solved problem number 3, 12.05 + 6.3?"
(Call on a student to explain.)

"Great explanation! What about problem number 4, 7.5 - 4.25?"
(Call on another student.)

"Excellent job today, everyone! I'll collect your worksheets now. Before you go, can you give me a thumbs up if you feel more confident adding decimals, and a thumbs down if you still have some questions? No worries either way, it helps me know what we need to work on next!"

(Collect worksheets. End with Decimal Dash Slide Deck - Slide 9)

"You all did a great job today. Remember, practice makes perfect when it comes to decimals. Keep an eye out for them in the real world!"