Subtraction can be a frustrating task for some students, especially when it comes to dealing with larger numbers. One method of subtraction that offers an alternative process is known as the "counting up" method. You can use this method to subtract or to check your work after having subtracted using the standard process. The counting up method involves viewing a subtraction problem from a perspective that focuses on adding.
Write out your subtraction problem. For example, you may have 327 - 168.
Figure out what must be added to the ones column of the smaller number to reach the next 10s number. In this example, you would add 2 to 68 to bring 68 up to 70. Write down the 2.
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Determine what must be added to the 10s column to reach the next hundreds place. In this example, you would have to add 30 to 170 to get 200. Write 30 underneath the 2 that you wrote in the previous step.
Add the value to the hundreds place to reach the same hundreds level as the larger number. In this example, you would have to add 100 to 200 to get 300. Write 100 underneath 2 and 30.
Add on the remainder in the larger number. In this example, you still have 27 left over once you've reached 300. Therefore, you would add 27 to the column containing 100, 30 and 2.
Add the numbers from your column for your final answer. In this example, you would add 27, 100, 30 and 2 to get 159.