Arithmetic Grade Five

Lesson Nine: Multiplication Review


You should be aware of two multiplication identities:
  1. Multiplying by 0: zero times any number is 0.
  2. Multiplying by 1: one times any number is that number.
Here are some examples:

  MULTIPLYING BY ZERO:
 
     5 x 0 = 0		0 x 9 = 0		121 x 0 = 0

    14 x 0 = 0		2 x 0 = 0		1 x 0 = 0

  MULTIPLYING BY ONE:

     5 x 1 = 5		12 x 1 = 12		1 x 9 = 9

     66 x 1 = 66	714 x 1 = 714		1 x 1 = 1

Multiplying by TEN is almost like an identity since calculating the product is so automatic. TEN x ANY NUMBER = ANY NUMBER WITH A ZERO AFTER IT. Here are some examples:

  MULTIPLYING BY TEN:
 
     5 x 10 = 50		10 x 9 = 90		121 x 10 = 1210

    14 x 10 = 140		2 x 10 = 20		1 x 10 = 10

One exception to this pattern is 10 x 0 = 0.

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