Subtraction

Subtraction is similar to addition in that you need to make sure you set up the problem lined up correctly.

697 minus 59 = ?

Also, as with addition, you need to start with the rightmost column and work your way left.

However, the big difference between subtraction and addition (other than the fact that you take away when subtracting and put together when adding, of course!) is that in subtraction you have to borrow rather than carry over as you do in addition. Borrowing means taking one from the column to the left and adding 10 to the column your’re working on. In the example problem above in the first column you need to subtract 9 from 7, but 7 is smaller than 9. This means you have to take 1 from the 9 to 7’s left and add ten to the ones column. Just slip a one in front of the seven to make it seventeen (7 +10). Since your taking one away from 9, you need to change it to an 8.

Now go on to the next column. You subtract 5 from 8 now since you borrowed over to the next column.

The resulting number of subtracting one number from another is called the difference. So 638 is the difference between 697 and 59.

There is one tricky thing you might encounter when subtracting: What if you need to subtract 147 from 5002?

Obviously since 7 is bigger than 2 you need to borrow. However the digit immediately to the left of the 2 is 0. This means you need to keep moving down to the left to find something to borrow from. The next digit is also 0. Keep moving. Finally you get to the five. Borrow from that to make it four. You need to carry that all the way through to the 2, so when you carry over to the first 0 you need to keep carrying over.

You need to keep carrying.

Now you can complete the operation.

 

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Comments

  • Kevin

    Perhaps make the 5002-147 a little less cluttered when showing the borrowing operation. As is it might confuse those who arent well versed in the art of subtraction.

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