N2C4TNp17

 

Answer to Problem 17:

+ , ´

 

DEFINITIONS:

commutative property of multiplication—the product stays the same when the order of the factors is changed. Example: 8 ´ 5 = 5 ´ 8.[1]

identity property of multiplication—if you multiply a number by one, the product is the same as the number.[2]

 

TEACHER NOTES:

Fourth graders should already know that when you switch the order of the factors when multiplying, the answer stays the same. They should also already be aware that when you multiply a number by one, the answer or multiple will be the same as the number. At this time, it would be good for them to begin to recognize the words that identify these happenings. It is also appropriate for them to begin exploring why changing the order in which you multiply two factors does not change the multiple or product. Similarly, they need to begin exploring why, when multiplying by 1, the result is the other factor.


 

[1] Math at hand: A mathematics handbook (p. 519). (1999). Wilmington, MA: Great Source Education Group, Inc.

[2] Cavanagh, M. (2000). Math to know (p. 526). Wilmington, MA: Great Source Education Group, Inc.