Three Digit Column Subtraction with One Regrouping

Working with three-digit numbers is no harder than working with two-digit or even one-digit numbers. When you solve a subtraction problem with numbers in the hundreds place (hundreds column), you just have to do it step-by-step.

But how about subtraction problems where the last digit of the top number is less (smaller) than the last digit of the bottom number? This is when you turn to regrouping (borrowing).

First, let's look at the ones place in the subtraction problem above. Can we subtract 8 from 1? No, we can't. We have to regroup from the tens place to give the ones place a two-digit value. (You will sometimes see the terms "ones column" and tens column" used.)

We cross out the 3 and write the new tens digit above it. This new tens digit is one less than the old digit.

We added the 1 ten that we regrouped to the ones place. Adding 1 ten makes the ones number a two-digit value. Look at the example below: 10 plus 1 equals 11 (10 + 1 = 11). We can now solve the problem.

Now we know that regrouping from the tens place gives the ones place a two-digit value. This helps us solve subtraction problems where the ones digit of the top number is less than the ones digit of the bottom number.

Let's look at another example:

Here we can see that 7 - 9 can't be solved. So we regroup 1 from the tens place. We add the 1 ten to 7, and it becomes 17. We also cross out the tens digit, 9, and write 8 above it. What does that mean? Well, regrouping 1 ten from 9 looks like this: 9 minus 1 (9 - 1). This leaves us with 8, which is the new tens digit.