Chapter 2

Test: Tuesday, Nov. 3

 

1. associative property - numbers stay in same order but use paranthesis to group, the sum stays the same

example: (3+4)+2=3+(4+2)

 

2. commutative property - numbers change order but the sum stays the same

example: 1+2+3=3+2+1

 

3. identity property - any number plus zero does not change the sum

example: 25+0=25

 

NEVER FIND THE REAL ANSWER!  Remember to round first then add or subtract

example: 325  becomes   300  Only find the rounded answer of 800

            +497               + 500

 

Remember the rule must work for all the problems. If the machine is "going backwards" make sure you do the opposite sign.

 

Example:  Rule: Add 25

35	To Figure Out (35+ 25)=60
100	To Figure Out (100+25)=125
To Figure Out (130-25)=105	130
To Figure Out (400-25)=375	400

 

 

 

REMEMBER THE DECIMAL POINTS MUST BE LINED UP BEFORE ADDING OR SUBTRACTING!

 

When subtracting, you may need to add zeroes as place holders so you can borrow.