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B.4 Add and subtract whole numbers: word problems

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What does it mean to add and subtract whole numbers?

Adding means finding the total or sum when you combine two or more numbers. Subtracting means finding how much is left or the difference when one number is taken away from another.

Examples:
  • 12 + 8 = 20 β†’ Add to find the total.
  • 35 βˆ’ 17 = 18 β†’ Subtract to find the difference.
Note

When you add, numbers get larger. When you subtract, numbers get smaller. Always check your operation before solving!

How to solve word problems using addition and subtraction

To solve word problems, carefully read each question to understand what is being asked. Decide whether you need to add or subtract, then show your work step by step.

Steps:
  • 1. Read the problem carefully.
  • 2. Identify what you know and what you need to find.
  • 3. Choose an operation (add or subtract).
  • 4. Solve using place value and regrouping if needed.
  • 5. Check your answer. Does it make sense?
Note

Look for clue words! Words like β€œin all,” β€œtotal,” and β€œcombined” often mean addition. Words like β€œleft,” β€œdifference,” and β€œhow many more” often mean subtraction.

Using place value to add and subtract accurately

When adding or subtracting multi-digit numbers, line up the digits by place value β€” ones under ones, tens under tens, and so on. This helps you regroup correctly and get accurate results.

Example:
  • 4,386 + 2,475 = 6,861
    Line up digits by place value and add each column.
  • 8,302 βˆ’ 4,187 = 4,115
    Subtract each place value carefully, regroup if needed.
Note

Always align numbers correctly before solving. Double-check each step, especially when regrouping tens, hundreds, or thousands.

Word problem examples

Let’s look at how addition and subtraction appear in real-life word problems.

Examples:
  • Maria collected 456 seashells in June and 389 in July. How many seashells does she have in all?
    456 + 389 = 845 seashells
  • A store had 2,350 pencils. They sold 1,275. How many pencils remain?
    2,350 βˆ’ 1,275 = 1,075 pencils
Note

Write a complete sentence for your answer. Example: β€œMaria has 845 seashells in all.” This helps explain your thinking clearly.

Checking your work

After solving, use the opposite operation to check your answer. This helps you confirm that your work is correct.

Example:
  • If 538 + 247 = 785, check with subtraction: 785 βˆ’ 247 = 538.
  • If 920 βˆ’ 415 = 505, check with addition: 505 + 415 = 920.
Note

Checking your work builds confidence and prevents simple mistakes. Always take a moment to review your final answer.