selma is now 3 times older than joyce . four years ago , selma was 4 times as old as joyce was then . find their present ages
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Answer:
There are four addition properties that help to add whole numbers :
For any whole number a, b, and c ;
1. <u>Closure property of addition </u>-
For example:
2+3=5
4+3=7
We can conclude that if we add any two whole number , we get another whole number.
2. <u>Associative property of addition</u>- when any whole number or variable are added, then that can be grouped in different way without changing result
For example:
2+(3+4)=(2+3)+4
3.<u> </u><u>Commutative property of addition</u>- when any whole number or variable are added, then the order changed without changing the result.
For example: 2+3=3+2
4. <u>Identity property of addition</u>- when 0 is added to a whole number or variable , the result is the same variable or number.
For example: 3+0=0+3
0 is called an Identity for addition of whole numbers.