Sadlier-Oxford Mathem

1. Chapter 2-11
Mental Math
October 15, 2012

2. Problem of the Day #9

3. 10-15-12
CHAPTER 2-11 commutative
associative property
Vocabulary property
mental math order grouping
1. associative (grouping) property - changing the
grouping of the addends (or factors) does not change the
sum (or product). 67 + 25 = ?
(60 + 7) + (20+5) = ?
(60 + 20) + (7+5) =
2. commutative property - Change the order of addends
(or factors) does not change the sum (or product)
3. mental math - being able to calculate quickly without
pen and paper
4. order - arrangement according to size, amount or
value (e.g. think greatest to least)
5. grouping - dividing things into equal groups (or
sets)

4. Associative (Grouping) Property Example
Same answer, which way was easier?

5. Chapter 2-11: Mental Math (TB page 83)
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6. Chapter 2-11: Mental Math (TB page 83)
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7. Chapter 2-11: Mental Math (TB page 83)
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8. Chapter 2-11: Mental Math (TB page 83)
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9. Chapter 2-11: Mental Math (TB page 83)
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