# Introducing Column Subtraction

by on December 14, 2011

If your child has been practicing his Subtraction Math Facts, then he will soon be moving on to Column Subtraction.  Column Subtraction is subtracting larger numbers (2-digit numbers such as 47 – 25) and writing them one on top of the other to put them into a column to subtract.

Be sure your child understands the concept of the Ones column and the Tens column, and that numbers in each of these columns are worth different values.  The column on the far right is the Ones, and the next one to its left is the Tens, and the next one moving left would be the Hundreds.  A “7” in the Ones column is simply worth 7, whereas a 7 in the Tens column is worth 70, and a 7 in the Hundreds column is actually worth 700.

At this beginning stage, your child will be given subtraction problems that do not require “regrouping”, or what you might refer to as “borrowing”.  I am going to list some sample problems to get you started.  PLEASE be sure to rewrite these subtraction problems in column format, one number on top of the other number!
1. 38 – 15

2. 79 – 48

3. 65 – 32

4. 96 – 74

5. 77 – 61

6. 84 – 62

7. 53 – 41

8. 28 – 13

9. 46 – 25

10. 75 – 23

Be sure to explain to your child that we always begin in the Ones column, or the column at the far right.  For problem #1, 38 – 15, he would first subtract 8-5 and write the answer, the “difference”, of 3 beneath the equals line.  Then, he would look at the Tens column, and subtract 3-1 and write 2 under the equals line.  He should see that his final answer is 23.  Ask him if he thinks this answer makes sense.  In other words, remind him that he is subtracting, so the numbers should be getting smaller as we are taking numbers away.  He started with 38, and he took 15 away, so it makes sense that his answer is smaller than 38.

Your child may very well be tempted to revert to using his fingers to count backwards while he is working through these problems.  Encourage him to use his Subtraction facts when possible.  If your child does not have a good handle on his Subtraction facts at this point, you will want to continue practicing those daily.

WANT MORE?

• As always, playing math games at home is a great way to reinforce math skills learned in school.