Decimal Dash! Script

Warm-Up: What's a Decimal? (5 minutes)

Teacher: "Good morning/afternoon everyone! Today, we're going on a 'Decimal Dash!' to learn all about adding and subtracting with these special numbers. Before we dive in, can anyone tell me, in your own words, what is a decimal? What do you think of when you hear the word 'decimal'?"




Teacher: "That's right! Decimals are simply parts of a whole number. Think about money – we use decimals all the time! If you have one dollar and fifty cents, you write it as $1.50. The '.50' is the decimal part, showing you have half of another dollar.

Today, we're going to focus on numbers that have a decimal point, like 2.35 or 5.75. We'll be looking at the tenths place, right after the decimal, and the hundredths place, which is two spots after the decimal."

Direct Instruction: Adding Decimals (8 minutes)

Teacher: "Alright, let's start with adding decimals. It's really not much different from adding whole numbers, but there's one super important rule we MUST follow. Take a look at Slide 2."

(Display Slide 2: Adding Decimals: Step 1)

Teacher: "The first and most important rule for adding decimals is to Line 'Em Up! You absolutely, positively, always have to line up the decimal points. Imagine the decimal points are like two magnets that want to stick together. If they're not lined up, your answer will be off."

(Display Slide 3: Adding Decimals: Step 2)

Teacher: "Once you have your decimal points lined up, all the other numbers will fall into place, lining up their correct place values – the ones, the tenths, the hundredths. Then, you just add like you normally would, starting from the right!"

(Display Slide 4: Let's Add!)

Teacher: "Let's try an example together. We have 2.35 plus 1.20. Watch carefully as I write it on the board."

(Write 2.35 + 1.20 vertically on the board, emphasizing lining up the decimal points.)

Teacher: "So, we start from the right: 5 + 0 equals 5. Then, 3 + 2 equals 5. Now, what do we do with that decimal point? That's right, we bring it straight down into our answer! And finally, 2 + 1 equals 3. So, 2.35 + 1.20 gives us 3.55. See? It's just like regular addition, but with that little dot!"

Direct Instruction: Subtracting Decimals (7 minutes)

Teacher: "Now that we've got adding down, let's tackle subtracting decimals. Guess what the most important rule is here?"

Teacher: "You got it! It's the exact same rule as addition! Take a look at Slide 5."

(Display Slide 5: Subtracting Decimals: Step 1)

Teacher: "Again, you must Line 'Em Up! Line up those decimal points first, and everything else will follow."

(Display Slide 6: Subtracting Decimals: Step 2)

Teacher: "Once your decimal points and place values are lined up, you subtract just like you always do. And remember, if you need more to subtract from, don't be afraid to borrow from the next place value! This is where it's exactly like subtracting whole numbers."

(Display Slide 7: Let's Subtract!)

Teacher: "Let's try an example: 5.75 minus 2.50. I'll write it on the board."

(Write 5.75 - 2.50 vertically on the board, emphasizing lining up the decimal points.)

Teacher: "Starting from the right: 5 minus 0 is 5. 7 minus 5 is 2. Bring that decimal point straight down! And 5 minus 2 is 3. So, 5.75 - 2.50 equals 3.25. Easy peasy, right?"

Guided Practice: Worksheet & Activity (7 minutes)

Teacher: "Excellent! You're all doing a fantastic job. Now it's your turn to get some practice in. I'm going to hand out a Worksheet: Decimal Dash Practice. I want you to work on the first few problems independently or with a partner. Remember our golden rule: line up those decimal points!"

(Distribute the worksheet. After a few minutes, introduce the activity.)

Teacher: "To help us really get the hang of lining up, we're also going to do a quick Activity: Decimal Line-Up Challenge. This will give you some hands-on practice making sure everything is in the right spot before you add or subtract. I'll be walking around to help anyone who needs it. When you're done, we'll quickly go over some of the answers using the Answer Key: Decimal Dash Practice."

(Circulate, provide support, and guide students. Facilitate the activity.)

Wrap-Up & Quick Check (3 minutes)

Teacher: "Alright everyone, let's bring it back together. You've worked hard on your decimal dash today!

Can one or two people share one new thing they learned about adding or subtracting decimals? Or maybe a helpful tip that you'll remember?"

Teacher: "Fantastic insights! To wrap up, here's a quick problem for you to solve on your own as an exit ticket. Solve this problem on a scrap piece of paper and hand it to me as you leave: 4.8 - 1.3 = ?"

(Write 4.8 - 1.3 = ? on the board. Collect exit tickets.)

Teacher: "Great work today, everyone! Keep practicing and you'll be decimal masters in no time!"

Decimal Dash Practice

Name: ____________________________

Date: _____________________________

Part 1: Adding Decimals

Remember to line up your decimal points! Show your work.

1. 4.25 + 1.30 =
   
   
   
   
   
   
   

2. 0.75 + 2.10 =
   
   
   
   
   
   
   

3. 12.6 + 3.2 =
   
   
   
   
   
   
   

4. 5.05 + 0.90 =
   
   
   
   
   
   
   

5. 8.1 + 1.75 =
   
   
   
   
   
   
   

Part 2: Subtracting Decimals

Remember to line up your decimal points! Show your work.

1. 6.85 - 2.30 =
   
   
   
   
   
   
   

2. 3.50 - 1.25 =
   
   
   
   
   
   
   

3. 9.7 - 4.1 =
   
   
   
   
   
   
   

4. 7.00 - 0.50 =
   
   
   
   
   
   
   

5. 10.25 - 5.1 =
   
   
   
   
   
   
   

Challenge Problem!

Sarah had $15.50. She bought a book for $7.25. How much money does she have left?

Decimal Line-Up Challenge!

Objective: To correctly line up decimal numbers for addition or subtraction, and to apply these skills to word problems.

Materials:

• Your Worksheet: Decimal Dash Practice (or separate scratch paper)
• Pencil

Instructions:

1. Work with a Partner (Optional): You can do this activity individually or with a partner.
2. Focus on Lining Up: For each problem below, your main goal is to write the numbers down correctly lined up before you even start solving.
3. Draw a Decimal Line: For extra help, draw a vertical line where the decimal points should be to keep them perfectly aligned.
4. Add Zeros if Needed: Remember, you can add zeros to the end of a decimal number without changing its value to help everything line up (e.g., 5.2 can be 5.20).

Challenge 1: Line Up for Addition!

Write these problems lined up, then solve them.

1. 1.7 + 0.35
   
   
   
   
   
   
   

2. 8.05 + 2.1
   
   
   
   
   
   
   

3. 6 + 3.42
   
   
   
   
   
   
   

Challenge 2: Line Up for Subtraction!

Write these problems lined up, then solve them.

1. 9.5 - 4.25
   
   
   
   
   
   
   

2. 7.30 - 1.8
   
   
   
   
   
   
   

3. 10 - 3.75
   
   
   
   
   
   
   

Challenge 3: Decimal Word Problems!

Read each problem carefully, set up your equation, line up your decimals, and solve!

1. Maria bought a drink for $1.75 and a snack for $2.50. How much did she spend in total?
   
   
   
   
   
   
   

2. A plant was 12.8 cm tall. It grew 3.2 cm more. How tall is the plant now?
   
   
   
   
   
   
   

3. A ribbon was 8.5 meters long. Sarah cut off 3.7 meters. How much ribbon is left?
   
   
   
   
   
   
   

Teacher Check-in: Once you've lined up and solved all the problems, have your teacher quickly check your alignment before you move on! You can then use the Answer Key: Decimal Dash Practice to check your answers.

Decimal Dash Practice Answer Key

Part 1: Adding Decimals

1. 4.25 + 1.30 = 5.55

   • Thought Process: Line up the decimal points. Add the hundredths (5+0=5), then the tenths (2+3=5). Bring down the decimal point. Add the ones (4+1=5).

     4.25
   + 1.30
   ------
     5.55
   

2. 0.75 + 2.10 = 2.85

   • Thought Process: Line up the decimal points. Add the hundredths (5+0=5), then the tenths (7+1=8). Bring down the decimal point. Add the ones (0+2=2).

     0.75
   + 2.10
   ------
     2.85
   

3. 12.6 + 3.2 = 15.8

   • Thought Process: Line up the decimal points. Add the tenths (6+2=8). Bring down the decimal point. Add the ones (2+3=5), then the tens (1+0=1).

     12.6
   +  3.2
   ------
     15.8
   

4. 5.05 + 0.90 = 5.95

   • Thought Process: Line up the decimal points. Add the hundredths (5+0=5), then the tenths (0+9=9). Bring down the decimal point. Add the ones (5+0=5).

     5.05
   + 0.90
   ------
     5.95
   

5. 8.1 + 1.75 = 9.85

   • Thought Process: Line up the decimal points, adding a zero to 8.1 to make it 8.10. Add the hundredths (0+5=5), then the tenths (1+7=8). Bring down the decimal point. Add the ones (8+1=9).

     8.10
   + 1.75
   ------
     9.85
   

Part 2: Subtracting Decimals

1. 6.85 - 2.30 = 4.55

   • Thought Process: Line up the decimal points. Subtract the hundredths (5-0=5), then the tenths (8-3=5). Bring down the decimal point. Subtract the ones (6-2=4).

     6.85
   - 2.30
   ------
     4.55
   

2. 3.50 - 1.25 = 2.25

   • Thought Process: Line up the decimal points. Subtract the hundredths (0-5, need to borrow from the tenths, making it 10-5=5). Subtract the tenths (4-2=2). Bring down the decimal point. Subtract the ones (3-1=2).

     3.5^410
   - 1.25
   ------
     2.25
   

3. 9.7 - 4.1 = 5.6

   • Thought Process: Line up the decimal points. Subtract the tenths (7-1=6). Bring down the decimal point. Subtract the ones (9-4=5).

     9.7
   - 4.1
   ------
     5.6
   

4. 7.00 - 0.50 = 6.50

   • Thought Process: Line up the decimal points. Subtract the hundredths (0-0=0). Subtract the tenths (0-5, need to borrow from the ones, making it 10-5=5). Bring down the decimal point. Subtract the ones (6-0=6).

     6^10.00
   -  0.50
   ------
     6.50
   

5. 10.25 - 5.1 = 5.15

   • Thought Process: Line up the decimal points, adding a zero to 5.1 to make it 5.10. Subtract the hundredths (5-0=5). Subtract the tenths (2-1=1). Bring down the decimal point. Subtract the ones (0-5, need to borrow from the tens, making it 10-5=5). Subtract the tens (0-0=0).

     10.25
   -  5.10
   ------
      5.15
   

Challenge Problem!

Sarah had $15.50. She bought a book for $7.25. How much money does she have left?

Answer: $8.25

• Thought Process: This is a subtraction problem. Line up the decimal points. Subtract the hundredths (0-5, borrow from the tenths, 10-5=5). Subtract the tenths (4-2=2). Bring down the decimal point. Subtract the ones (5-7, borrow from the tens, 15-7=8). Subtract the tens (0-0=0).

    1^05.^410
  -  7.25
  ------
    $8.25
  ```<br/><br/><br/># Decimal Line-Up Challenge Answer Key
  

Challenge 1: Line Up for Addition!

1. 1.7 + 0.35 = 2.05

     1.70
   + 0.35
   ------
     2.05
   

2. 8.05 + 2.1 = 10.15

     8.05
   + 2.10
   ------
    10.15
   

3. 6 + 3.42 = 9.42

     6.00
   + 3.42
   ------
     9.42
   

Challenge 2: Line Up for Subtraction!

1. 9.5 - 4.25 = 5.25

     9.5^410
   - 4.25
   ------
     5.25
   

2. 7.30 - 1.8 = 5.50

     7.^2130
   - 1.80
   ------
     5.50
   

3. 10 - 3.75 = 6.25

     9^10.^9100
   -  3.75
   ------
     6.25
   

Challenge 3: Decimal Word Problems!

1. Maria bought a drink for $1.75 and a snack for $2.50. How much did she spend in total?
   Answer: $4.25

   • Thought Process: This is an addition problem. Line up the decimal points.

     $1.75
   + $2.50
   ------
     $4.25
   

2. A plant was 12.8 cm tall. It grew 3.2 cm more. How tall is the plant now?
   Answer: 16.0 cm (or 16 cm)

   • Thought Process: This is an addition problem. Line up the decimal points.

     12.8
   +  3.2
   ------
     16.0
   

3. A ribbon was 8.5 meters long. Sarah cut off 3.7 meters. How much ribbon is left?
   Answer: 4.8 meters

   • Thought Process: This is a subtraction problem. Line up the decimal points and borrow as needed.

     7^8.5^15
   - 3.7
   ------
     4.8