Foundations of Multi-Digit Subtraction

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What is the most important first step when you write down a multi-digit subtraction problem?

Line up the numbers vertically so that the ones, tens, hundreds, and other place values are in the same columns.

In which place value column do you always begin subtracting?

You always start subtracting in the ones column, which is on the far right.

What is the minuend in a subtraction problem?

The minuend is the first number in a subtraction problem—the number from which you are subtracting. In $10 - 4 = 6$, the minuend is $10$.

What is the subtrahend in a subtraction problem?

The subtrahend is the number being subtracted from another number. In $10 - 4 = 6$, the subtrahend is $4$.

If the top digit in a column is larger than the bottom digit, do you need to regroup?

No. If the top digit (from the minuend) is larger, you can subtract directly.

$$ 487 - 235 = ? $$

Line up the numbers.$$\begin{array}{rr} & 487 \\ - & 235 \\ \hline & 252 \end{array}$$Ones: $7 - 5 = 2$ Tens: $8 - 3 = 5$ Hundreds: $4 - 2 = 2$ The answer is $252$.

$$ 999 - 123 = ? $$

$$\begin{array}{rr} & 999 \\ - & 123 \\ \hline & 876 \end{array}$$Ones: $9 - 3 = 6$. Tens: $9 - 2 = 7$. Hundreds: $9 - 1 = 8$. The answer is $876$.

What is the difference between $876$ and $345$?

The word 'difference' signals subtraction. $876 - 345 = 531$.

$$ 568 - 142 = ? $$

$426$

When setting up the problem $345 - 21$, how do you align the numbers?

You place the $345$ on top. The $21$ goes below, with the $1$ under the $5$ (ones place) and the $2$ under the $4$ (tens place).