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Solving 3-Digit Word Problems

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Lesson Plan

Solving 3-Digit Word Problems

Students will be able to solve one-step addition and subtraction word problems with 3-digit numbers by identifying the operation and performing the calculation accurately.

Mastering word problems helps students apply math to real-life situations, building confidence and critical thinking skills essential for future mathematical understanding.

Audience

2nd Grade

Time

15 minutes

Approach

Guided practice with a focus on problem-solving strategies.

Materials

One-Step Word Problem Warm-Up (#one-step-word-problem-warm-up), Solving 3-Digit Word Problems Slide Deck, Practice Word Problems Worksheet, Answer Key, and Cool Down: Problem Solve!

Prep

Review Materials & Customize

5 minutes

Step 1

Warm-Up: Problem Detectives

3 minutes

  • Begin with the One-Step Word Problem Warm-Up to activate prior knowledge on identifying operations in word problems.
    * Discuss student responses, emphasizing keywords that signal addition or subtraction.

Step 2

Introduction to 3-Digit Problems

2 minutes

Step 3

Guided Practice:

60 minutes

Warm Up: Problem Detectives (5 minutes)
* Teacher Script:

Step 4

Independent Practice: Problem Solvers

8 minutes

  • Distribute the Practice Word Problems Worksheet.
    * Students work independently to solve the word problems. Circulate to provide individualized support and clarification.
    * Remind students to show their work and identify whether they are adding or subtracting.

Step 5

Cool-Down: Share Your Strategy

2 minutes

  • Conclude with the Cool Down: Problem Solve! where students reflect on a strategy they used to solve a word problem.
    * Briefly discuss a few student responses to reinforce learning and different problem-solving approaches.
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Slide Deck

Welcome, Math Detectives!

Today, we're going to become super solvers!

Welcome students and set a positive tone. Explain that today we'll be tackling some exciting math challenges.

Numbers are Getting Bigger!

We've solved problems with 1-digit and 2-digit numbers.

Now, let's look at 3-digit numbers!

(Like 123, 456, 789)

Introduce the idea of word problems involving bigger numbers. Emphasize that the strategies are the same, just the numbers are larger.

Quick Review: Place Value

Remember hundreds, tens, and ones?

  • Hundreds (like the '1' in 150)
  • Tens (like the '5' in 150)
  • Ones (like the '0' in 150)

Review place value as a quick refresher. This is crucial for 3-digit number operations.

When Do We ADD?

Look for words like:

  • In all
  • Altogether
  • Sum
  • Total
  • Plus
  • And
  • Combine

Remind students about keywords for addition. Ask them to shout out any they remember.

When Do We SUBTRACT?

Look for words like:

  • Difference
  • How many more
  • Left
  • Remain
  • Minus
  • Take away

Remind students about keywords for subtraction. Ask them to shout out any they remember.

Let's Solve Together!

Problem 1:

Mr. Chen had 345 pencils. He bought 120 more pencils.

How many pencils does Mr. Chen have in all?

Present the first practice problem. Guide students through identifying keywords and setting up the problem.

Solution to Problem 1

Keywords: "in all", "bought more" -> ADDITION!

345

  • 120

465

Mr. Chen has 465 pencils in all.

Reveal the solution step-by-step. Show how to line up the numbers and perform the addition.

Another Problem!

Problem 2:

There were 587 birds in a tree. 235 birds flew away.

How many birds are left in the tree?

Present the second practice problem. Guide students through identifying keywords and setting up the problem.

Solution to Problem 2

Keywords: "flew away", "left" -> SUBTRACTION!

587

  • 235

352

There are 352 birds left in the tree.

Reveal the solution step-by-step. Show how to line up the numbers and perform the subtraction.

Your Turn to Be a Solver!

Now you'll get to solve some problems on your own!

Remember to:

  • Read carefully.
  • Look for keywords.
  • Decide if you add or subtract.
  • Show your work!

Transition to independent practice. Encourage students to use the strategies they just reviewed.

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Warm Up

One-Step Word Problem Warm-Up

Directions: Read each word problem carefully. Circle the keywords that tell you whether to ADD or SUBTRACT. You do not need to solve the problem, just identify the operation!

  1. There were 15 apples on a tree. 7 apples fell off. How many apples are left on the tree?

    • Operation:


  2. Maria has 23 stickers. Her friend gave her 12 more stickers. How many stickers does Maria have in all?

    • Operation:


  3. A baker made 50 cookies. He sold 30 cookies. What is the difference between the number of cookies he made and the number he sold?

    • Operation:


  4. David collected 45 seashells. His brother collected 38 seashells. How many seashells did they collect altogether?

    • Operation:


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Worksheet

Practice Word Problems Worksheet: 3-Digit Numbers

Directions: Read each word problem carefully. Show your work in the space provided and write your answer clearly.

  1. The school library had 452 adventure books. They received 135 new adventure books. How many adventure books do they have in all?

    • Show your work:






    • Answer:



  2. A farmer planted 678 corn seeds. 243 of the seeds did not grow. How many corn seeds grew?

    • Show your work:






    • Answer:



  3. Sarah counted 319 butterflies in her garden on Monday. On Tuesday, she counted 170 more butterflies. What is the total number of butterflies Sarah counted?

    • Show your work:






    • Answer:



  4. There were 895 people at the fair on Saturday. 561 people left before dinner. How many people remained at the fair?

    • Show your work:






    • Answer:



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Answer Key

Answer Key

One-Step Word Problem Warm-Up

  1. There were 15 apples on a tree. 7 apples fell off. How many apples are left on the tree?

    • Operation: SUBTRACT

  2. Maria has 23 stickers. Her friend gave her 12 more stickers. How many stickers does Maria have in all?

    • Operation: ADD

  3. A baker made 50 cookies. He sold 30 cookies. What is the difference between the number of cookies he made and the number he sold?

    • Operation: SUBTRACT

  4. David collected 45 seashells. His brother collected 38 seashells. How many seashells did they collect altogether?

    • Operation: ADD

Practice Word Problems Worksheet: 3-Digit Numbers

  1. The school library had 452 adventure books. They received 135 new adventure books. How many adventure books do they have in all?
    • Thought Process: The keyword
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Cool Down

Cool Down: Problem Solve!

Directions: Think about the word problems you solved today. What was one strategy you used to figure out if you needed to add or subtract? Explain it in your own words.












Bonus: Write one word problem using a 3-digit number and either addition or subtraction. You don't need to solve it, just write the problem!












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Solving 3-Digit Word Problems • Lenny Learning