Page 9 - prim 4 كامل

Delta Modern Language Schools
Maths Department
Prim 4 2023-2024

Unit 2: addition and subtraction strategies

1) Properties of addition and subtraction
a) Additive identity property

Ex.: 0 + 6578 = 6578 and 1024 + 0 = 1024
( Any number + 0 = the same number )

b) Commutative property
Ex.: 5 + 2 = 2 + 5
(Order of numbers in addition doesn’t important)

c) Associative property
Ex.: ( 5 + 2 ) + 3 = 5 + ( 2 + 3 )
(Solve what in the parentheses first)
Note: These properties doesn’t apply in subtraction.

2) Mental math strategies
a) Front-end estimation:

Ex. : 176 – 94
100 – 90 = 10

May not be close to the actual answer
b) Rounding:

Ex.1 : 176 – 94
180 – 90 = 90

More accurate estimate

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