## Double Digit Addition and Subtraction

#### Aligned To Common Core Standard:

**Grade 2 Base Ten** - 2.NBT.5

Here are some tips for adding and subtracting double digit numbers :
After learning simple single-digit addition and subtractions, kids need to proceed to double-digit addition and subtraction. A child with a perfect understanding of single-digit addition and subtraction can easily understand the double-digit addition and subtraction. Here are some effective tips that will help kids develop strong concepts of double-digit addition and subtraction.
**Using Number Lines** - Kids can efficiently add and subtract double-digit numbers using a number line. If they are aware of concepts of skip counting, using a number line can significantly help them.
**Using Base 10 Blocks** - Another tips that can help children quickly learn double-digit addition and subtraction is to use the base 10 blocks. It helps kids add numbers beyond 100 with ease.
**Ungrouping** - Place value can ease the addition and subtraction for the kids. Breaking a number in tens or ones can help kids efficiently subtracting complicated double-digit numbers.
**Count Down, Count Up** - When the concept of counting up and counting down is clear, a student can easily solve double-digit addition and subtraction problems.
The goal of these worksheets is achieve mastery of adding and subtracting double digit integers.

### Double Digit Addition and Subtraction Worksheets And Lessons

- Step-by-step Lesson- We run you
through everything in this lesson. Single and double digit sums,
double digit differences and sums.

- Guided Lesson - Horizontal
and vertical double digit differences and sums. We follow that with
a simple image based problem.

- Guided Lesson Explanation
- You could also just have the students rewrite the numbers in a
horizontal format, if that helps.

- Practice Worksheet - More
double digit basic operations. They are all aligned vertically.

- Matching Worksheet - Match the horizontal sum of difference with its equation.

#### Homework Sheets

This skill, by most past state standard fell into grade 3, but now it is a grade 2 skill.

- Homework 1 - We overexaggerate the spacingf to help students stay lined up and orderly.
- Homework 2 - The operations alternate as you move through the problems.
- Homework 3 - In this particular worksheet we also alternate the need to borrow or regroup.

#### Practice Worksheets

I threw in a matching format to make it a little bit more fun for the kids.

- Practice 1 - Match the equations to the end sum or difference.
- Practice 2 - Write the letter of the sum or difference on the line.
- Practice 3 - We step up to working these operations with three digit numbers. This is here to see if students are ready for the next level.

#### Math Skill Quizzes

There is a good bit of number carrying going on here.

- Quiz 1 - It is time to see if you understand this skill.
- Quiz 2 - We focused on the spacing here for students that are still having difficulty with this.
- Quiz 3 - Expect a good amount of regrouping with this quiz.

### How to Add Double Digit Values (with Regrouping)

When you are finding the sum of two values that consist of double digits it requires several skills, but above all it is essential that you stay organized throughout the entire process. In the example below we will introduce you to the concept of regrouping. Regrouping is just moving a value between place values. In the case of addition, we are moving an overloaded values in the ones place up to the tens placed. We will now explore an example of this by finding the sum of 37 and 28.

#### Solution

**Step 1)** Add the values in the one place (7 + 8 = 15).

**Step 2)** This resulted in a value (15) that is greater than 9. This value is too large to fit at the ones value. This is where regrouping comes in handy. We can move that tens value up one column. As a result, we must carry the tens digit (1) to the tens place of question and drop the ones digit (5) into the ones place of our answer (sum).

**Step 3)** We complete the problem by adding all the values (1 + 3 + 2 = 6) in the tens place. We just write the final sum (65) at the bottom.

### How to Subtract Double Digit Values (with Borrowing)

The regrouping method also applies in subtraction, but it occurs in reverse. The regroup happens on the minuend when the ones values are underfunded. You can move a tens value down to the ones place to satisfy your difference. We call this method borrowing which makes sense because you are borrowing a value from one place to help another. Explore the subtraction problem (42 - 27) that we have worked through below.

#### Solution

**Step 1)** Subtract the ones place. In this case (2 - 7), we cannot complete this difference because the difference would bring us a result that is less than zero. This where we can borrow from the tens place. We will reduce the tens place of the minuend by 1 (4 - 1 = 3). We can then transfer this ten to the ones place (10 + 2 = 12). We can now subtract the ones place (12 – 7 = 5).

**Step 2)** Now that we have our problem in order, we can simply subtract the remaining tens place (3 - 2 = 1) and drop that difference into the answer of our difference. The final answer is a difference of 15.