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U.1 Break apart a one-digit number to subtract

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What is subtraction with two-digit numbers?

Subtraction is taking away one number from another to find the difference. When subtracting a one-digit number from a two-digit number, we can use strategies to make it easier.

Example:
  • 54 − 7 = ?
Note

Always begin with the larger number and subtract the smaller number to find the difference.

What is the break apart strategy?

The break apart strategy means splitting the smaller number into parts to subtract step by step. This makes subtraction easier to do in your head or on paper.

Steps:
  • Take the two numbers: 54 − 7
  • Break apart 7 into 4 and 3
  • Subtract 4 first: 54 − 4 = 50
  • Subtract the remaining 3: 50 − 3 = 47
Note

Breaking apart helps when subtracting across a tens place. It makes the work simpler and reduces mistakes.

More examples using break apart

Here are some examples of how to use the break apart strategy when subtracting a one-digit number from a two-digit number:

Examples:
  • 62 − 8 → break 8 into 2 and 6 → 62 − 2 = 60 → 60 − 6 = 54
  • 47 − 5 → break 5 into 2 and 3 → 47 − 2 = 45 → 45 − 3 = 42
  • 81 − 9 → break 9 into 1 and 8 → 81 − 1 = 80 → 80 − 8 = 72
Note

Choose the numbers you break apart so that you land on a “friendly number” like 50, 60, 70, or 80. Friendly numbers make subtraction easier.

Using subtraction in sentences

We can use subtraction to solve story problems in real life. Practice writing and solving subtraction in words to better understand how it works.

Examples:
  • Maria had 54 apples. She gave 7 away. How many apples does she have left?
    54 − 7 = 47
  • Sam had 62 toy cars. He lost 8. How many toy cars are left?
    62 − 8 = 54
  • A class had 81 pencils. They used 9. How many pencils are still there?
    81 − 9 = 72
Note

Always check your work by adding your answer to the smaller number. If it equals the larger number, your subtraction is correct.

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