How to Use Addition to Check Subtraction

Checking Single Digit Subtraction Problems With Addition

• 1

  Find the difference between two numbers in a subtraction problem. Write the answer again to begin an addition sequence.

  (Initial subtraction problem) 8 - 5 = 3

  (Checking answer with addition) 3

• 2

  Write the digit subtracted from the first number in the initial subtraction problem into the new addition problem. Place an "equals" sign after writing the second number.

  (Initial subtraction problem) 8 - 5 = 3

  (Checking answer with addition) 3 + 5 =

• 3

  Add the two digits together.

  (Initial subtraction problem) 8 - 5 = 3

  (Checking answer with addition) 3 + 5 = 8

• 4

  Compare the answer found with the first number in the subtraction problem.

  8 = 8 CORRECT!

  Matching numbers mean that the subtraction difference is correct.

Checking Two-Digit Subtraction Problems With Addition

• 5

  Compute the answer to a two-digit subtraction problem.

  89 - 14 = 75

  Write the answer whose accuracy you wish to check to begin another operation sequence.

  89 - 14 = 75

  75

• 6

  Rewrite the second number from the subtraction problem with an addition sign and an "equals" symbol.

  89 - 14 = 75

  75 + 14 =

• 7

  Add the two numbers together and write the answer to the equation.

  89 - 14 = 75

  75 + 14 = 89

• 8

  Compare the findings of the addition problem with that of the first number in the subtraction problem. Matching numbers confirm the correct answers.

  89 = 89 CORRECT!