24. Roman System
•Additive system
•Subtractive property – if a smaller symbol is to
the left of a larger symbol, it is subtracted from
the larger
•No more than three of the same symbol in a row
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32. Properties of whole-number addition
Commutative Property of Addition
a+b=b+a
2+1=1+2
Associative Property of Addition
(a + b) + c = a + (b + c)
(4 + 3) + 7 = 4 + (3 + 7)
Identity Property of Addition
a+0=a
7+0=7 0 is the additive identity
33. Whole Number subtraction
5–2=3
minuend subtrahend difference
Subtraction is related to addition:
5 – 2 = 3 if 5 = 2 + 3
34. Models for whole-number subtraction
5–2=3
Start with 5 stars
Take-away Model Take away 2
3 stars left
35. Models for whole-number subtraction
5–2=3
Start with 5 stars
Comparison Model Compare with 2 circles
3 stars left