Students realize the commutative property of addition and that it does not apply to subtraction.
Use concrete objects in each case to explore and analyze.
Students compare pairs of numbers added together, such as 3 + 5 and 5 + 3, 2 + 4 and 4 + 2, etc., and conjecture about whether or not the sum is always the same, even if they switch the order of the addends.
Students compare switching the numbers in a subtraction problem, such as 5 – 3 and 3 – 5, to see if the difference changes or remains the same.
In a whole-class discussion, clarify and make clear the mathematics property.