Numbers

3-36 Mental Math Methods, Addition

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Mental math is doing math in your head.   You can group addends to help you find the sum.

 

Parentheses may be used without changing the sum.

(5 + 3) + 6 = 14 and 5 + (3 + 6) = 14

 

The order of the addends doesn't change the sum.

3 + 4 = 7 and 4 + 3 = 7

 

When you add many numbers together, use one of these ways to help you.

To find the sum of 6 + 4 + 3 + 7 + 2 group them in the easiest way.

6 + 4 = 10 and 3 + 7 = 10, so 10 + 10 + 2 = 22

 

Practice mental math methods.  Fill in the sums.

 

3 + 7 + 5 + 6 + 9 =
9 + 5 + 1 + 1 + 9 =
 
13 + 1 + 7 + 2 =
 
21 + 4 + 10 + 10 =
 
19 + 5 + 1 + 5 =
 
8 + 1 + 10 + 9 =
 
7 + 5 + 4 + 4 =
 
6 + 6 + 6 + 2 =
 
11 + 4 + 4 + 2 =
 
12 + 7 + 1 =
 
14 + 5 + 6 + 2 + 3 =
 
9 + 6 + 6 + 9 =
 
13 + 10 + 2 =
 
1 + 9 + 22 =
 
5 + 15 + 15 =

 

 

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