1. Mental Math Tricks

2. Properties of addition of natural numbers Result of an addition is called a SUM Addition is a commutative operation a+b=b+a Order does NOT MATTER Example: 34+53=87 53+34=87 34+53=53+34

3. Properties of addition Addition is associative (a+b)+c=a+(b+c) What do brackets mean? We have to do that operation first Example: 3+(4+9)= 3+(13) =16

4. Properties of addition Associative means that (3+4)+9 also works Brackets first, (3+4)+9= (7)+9= 16 3+(4+9)=(3+4)+9

5. Properties of addition Neutral element of addition. Any number plus zero. Example: a+0=a 14+0=14

6. Properties of Subtraction Result of a subtraction is called a difference Commutative and Associative Properties DO NOT WORK Example 34-35=-1 NOT A NATURAL NUMBER 35-34=1 Both equations are not the same! In subtraction order Matters!

7. Example Verify the commutative property of addition a+b=b+a If a=200 and b=98

8. Example Verify the associative property of addition (a+b)+c=a+(b+c) If a=23 B=45 c=40

9. Homework Math 300 Page 10 #1 Pg 11#3, 5,6 Pg 12 #8,9,10 Pg 13 #14