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Find and correct a subtraction error

Subtraction errors are interpreted through place value and the meaning of the difference in whole-number problems within 1,000, including cases requiring regrouping across ones, tens, or hundreds. Correcting an error involves locating the step where place-value units were exchanged or subtracted incorrectly, then confirming the revised result with an addition equation, a number line, or an estimate; more advanced numbers, decimals, negative numbers, and generalized error analysis are not included.

Detailed Explanation: Find and correct a subtraction error

When you find a subtraction error, check each place value: ones, tens, and hundreds. Look for a place where regrouping was needed but was missed or done incorrectly.

Example:

542− 268324\begin{array}{r} 542\\ -\ 268\\ \hline 324 \end{array}

The answer 324324 is incorrect. Let’s find the error.

  1. Check the ones.
    We cannot subtract 88 ones from 22 ones, so regroup 11 ten as 1010 ones:

    • 542542 becomes 55 hundreds, 33 tens, and 1212 ones.
    • 12−8=412-8=4 ones.

  2. Check the tens.
    Now we have 33 tens, but we cannot subtract 66 tens from 33 tens. Regroup 11 hundred as 1010 tens:

    • 55 hundreds becomes 44 hundreds.
    • 33 tens becomes 1313 tens.
    • 13−6=713-6=7 tens.

  3. Check the hundreds.

    • 4−2=24-2=2 hundreds.

So the correct difference is

542− 268274\begin{array}{r} 542\\ -\ 268\\ \hline 274 \end{array}

The error was in the tens place: the 33 tens needed to be regrouped with 11 hundred before subtracting 66 tens.

Check the answer with addition:

274+268=542274+268=542

Because the sum matches the starting number, 274274 is the correct difference.

Learn by doing: Find and correct a subtraction error

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    Subtraction - Whole Number 3 x 2, With Borrow

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