You have learned that when you subtract one number from another, you find the difference (answer) between them. Some numbers are so small that they are easy to subtract, even if you're counting on your fingers. But when you're dealing with greater (larger) numbers, you need to know a better way to subtract. When we are doing subtraction with numbers that are greater than 10, it is a good idea to use column subtraction.
Here's how it works. First, write down the greater number. Then, below it, write the lesser (smaller) number. When subtracting numbers, be sure to line up the place values. Make sure that the last digit of the second number is right below the last digit of the first number.
Write a minussign to the left of the lesser number. Then, under the bottom number, write a line going across. This is an equal bar. You will write the difference (answer) under this bar.
If you were trying to solve the problem 68 minus 47 (68 - 47), here's how you would write it as a column subtraction problem:
Now it's time to solve the problem. Look at the place value on the far right. This is called the ones place (ones column). The first thing you should do is subtract the ones place. In the example, the numbers in the ones place are 8 and 7. What is 8 minus 7 (8 - 7)? It equals 1. Write "1" in this ones column under the equal bar.
Next, you will subtract the tens place (tens column) on the left. What is 6 minus 4 (6 - 4)? It equals 2. Write "2" in this tens column under the equal bar.
You've solved the problem! The difference of 68 minus 47 equals 21 (68 - 47 = 21).
