Subtracting with Digits Up to 1000

Subtracting with digits up to 1000 means working with numbers that have up to three digits, like hundreds, tens, and ones, and finding the difference between them. This skill builds directly on smaller subtraction problems and sets students up for more advanced strategies later on. Once students are comfortable subtracting hundreds, tens, and ones, three digit subtraction becomes a matter of following the same steps every time.

Every number up to 1000 can be broken into hundreds, tens, and ones. For example, 673 is 6 hundreds, 7 tens, and 3 ones. When subtracting two numbers, the first step is always to line them up so that hundreds sit above hundreds, tens sit above tens, and ones sit above ones. This keeps each digit paired with the correct place value and avoids mixing up columns.

Students who are still building this foundation may find it helpful to review Subtraction with Tens and Ones first, since three digit subtraction simply adds a hundreds column to the same idea.

The standard method for subtracting numbers up to 1000 always works from right to left:

1. Subtract the ones column first.
2. Subtract the tens column next.
3. Subtract the hundreds column last.

Using the example above, \( 673 - 241 \): the ones column gives \( 3 - 1 = 2 \), the tens column gives \( 7 - 4 = 3 \), and the hundreds column gives \( 6 - 2 = 4 \). Reading the answer from left to right gives \( 673 - 241 = 432 \).

Sometimes the top digit in a column is smaller than the bottom digit, such as in \( 502 - 168 \), where the ones column needs \( 2 - 8 \). In these cases, a digit must be borrowed, or regrouped, from the column to its left before subtracting. This regrouping step is common in 3 digit subtraction with regrouping, and it deserves its own careful practice. For a full walkthrough of borrowing across hundreds, tens, and ones, see Subtraction with Regrouping Up to 1000.

A subtraction answer can always be checked by adding it back to the number that was subtracted. For \( 673 - 241 = 432 \), checking means confirming that \( 432 + 241 = 673 \). If the two sides do not match, one of the columns was subtracted incorrectly and it is worth working through the problem again.

Before checking with addition, it also helps to estimate the answer first by rounding each number to the nearest hundred. Rounding 673 to 700 and 241 to 200 gives an estimate of about 500, which is close to the actual answer of 432 and confirms the answer is reasonable. This kind of quick check is explored further in Subtraction using Estimation.

Find \( 845 - 523 \).

Ones column: \( 5 - 3 = 2 \).
Tens column: \( 4 - 2 = 2 \).
Hundreds column: \( 8 - 5 = 3 \).

So \( 845 - 523 = 322 \). Checking with addition, \( 322 + 523 = 845 \), which matches, so the answer is correct.

With steady practice lining up place values and working through each column in order, subtracting any two numbers up to 1000 becomes a reliable, repeatable process.

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