In this post, we are going to learn a** mental math trick for adding and subtracting various numbers**. It’s all about grouping the numbers that can give us exactly ten. In order to do so, we really need to pay attention to the numbers.

##### Mental Math: Addition

In order to add, we need to see if the problem we’re working on has any of these pairs:

1 + 9 = 10

2 + 8 = 10

3 + 7 = 10

4 + 6 = 10

5 + 5 = 10

6 + 4 = 10

7 + 3 = 10

8 + 2 = 10

9 + 1 = 10

For example:

5 + 6 + 5 + 1

If we look at the problem, we see 5 + 5 = 10. After, we only have to add the rest of the numbers: 10 + 6 + 1 = **17**

Let’s look at another example:

12 + 14 + 18

In this problem, we first add 12 + 18 = 30, and after 30 + 14 = **44**

##### Mental Math: Subtraction

In order to subtract, we have to look for the numbers that give us exactly 10 when we subtract them.

For example:

16 – 4 – 6

First we subtract 16 – 6 = 10, and after 10 – 4 = **6**

Let’s look at another example:

38 + 15 – 18

We’ll first subtract 38 – 18 = 20, and then add 20 + 15 =** 35**

By solving this way, we can add and subtract various numbers more easily. Also check out different strategies for mental calculation from Smartick!

### Learn More:

- Strategy for Mental Calculation: Add and Subtract Numbers
- Mental Calculation: Horizontal Addition and Subtraction
- Strategies for Solving Incomplete Horizontal Additions and Subtractions
- Learn to Subtract with Remainders
- Learn How to Subtract with Examples

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