Math Skill: Mental Addition and Subtraction to 100
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Mental Addition and Subtraction to 100

You must know fast addition and subtraction to master this topic.
To review, see the Fast Addition and Fast Subtraction topics.

When adding or subtracting 10, just calculate the tens column.
If you borrow or carry, then calculate the hundred column.

 38 +10 48

 52 +10 62

 90 +10 100

Example 2: Subtraction

 44 -10 34

 74 -10 64

 98 -10 88

 1.   39 + 10 = 2.   26 + 10 =

 1.   90 + 10 = 2.   38 + 10 =

### Complexity=40, Mode=sub

Subtract.
 1.   15 - 10 = 2.   11 - 10 =

### Complexity=90, Mode=sub

Subtract.
 1.   61 - 10 = 2.   81 - 10 =

### Complexity=40

 1.   38 + 10 = 2.   10 - 10 =

### Complexity=90

 1.   43 - 10 = 2.   33 - 10 =

139 + 10 =
Solution
226 + 10 =
Solution

190 + 10 =
Solution
```  1
90
+  10
100
```
238 + 10 =
Solution

Subtract.
115 - 10 =
Solution
211 - 10 =
Solution

Subtract.
161 - 10 =
Solution
281 - 10 =
Solution

138 + 10 =
Solution