Adding Double Digit Numbers

When your child began learning how to add, they initially began practicing this skill by adding single digit numbers. The sum of those single digit numbers could either be another single digit number, or it could turn into a double digit number. While no sum of two single digit numbers can exceed the number 18, adding two double digit numbers opens up an endless number of possibilities.

Adding Double Digit Numbers

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  1. When adding two double digits together, you must begin on the right side of the equation and move to the left. One easy way to help your child learn how to add double digit numbers is for them to see the two pairs of numbers as separate equations. That is, as 73 and 48 are being added together, it will be easier to view the equation as 7 and 4, and 3 and 8 being added together.
  2. Beginning from right to left, first find the sum of the right side of the equation. Notice that since the sum of 3 and 8 is 11, there is a “1” underneath the right side of the equation. However, with the “leftover” 1, you must carry it over to the left side of the equation and add it to this side of the equation. You will see that the 7 plus 4 has now become an 8 plus 4.
  3. Finally, find the sum of the “new” equation, 8 plus 4, and write down the sum of this equation adjacent to the previous sum you found. The resulting sum of 73 and 48 is 121.

A general rule of thumb for your child to remember when doing these double digit addition equations is that they must do the equation from right to left. While not all equations will require your child to carry over a 1 to the other side of the equation, help your child to remember this specific tip just in case they need to carry over the 1. Also, when finding the sum of the left side of the equation, remember that there is no need to “carry over” another digit. Because there is no other number in the thousands place in this equation, the sum of the equation on the left side can be written as is.

Use this article as a resource to help your child learn their double digit addition skills at a step-by-step pace.



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