Multiplication

Multiplication

(At the bottom of the page is a printable of Multiplication help notes.)

In our Multiplication unit we will be learning about how to multiply using the expanded algorithm, along with arrays, properties of multiplication, factors, composite and prime numbers, and multiples.

 Multiplication is a simpler way to do repeated addition.  For example: 4 x 6 is easier than 4 + 4 + 4 + 4 + 4 + 4.  You are also less likely to make a careless error using multiplication than if you use repeated addition.

 An array is a way of ordering objects in rows and columns to make a rectangular shape.  In an array, all the rows are equal to each other and all the columns are equal to each other and that makes a rectangular shape.  For example:

 The zero property of multiplication is that any factor multiplied by 0 equals 0.  For example: 5 x 0 = 0

 The identity property of multiplication is that any factor multiplied by 1 equals the original factor.  For example: 3 x 1 = 3

 The commutative property of multiplication is that two factors can be multiplied in either order and give the same answer.  For example: 7 x 2 = 2 x 7

 The associative property of multiplication is that three or more factors can be multiplied in different groups and still give the same answer.  For example: (4 x 5) x 6 = 4 x (5 x 6)

  A number is a factor of another number if it divides into it evenly without a remainder.  To find factors of a number you can make a factor rainbow.  See the example below:  The factors of 24 are 1, 2, 3, 4, 6, 8, 12, and 24.

                                                                                           1  2  3  4                        6  8 12 24

 Prime numbers are numbers that can only be divided evenly by 1 and themselves.  For example:  7 is a prime number because it only has 2 factors.  These factors and 1 and 7.

 Composite numbers are numbers that have more than 2 factors.  For example: 4 is a composite number because its factors are 1, 2, and 4.

 Since 0 has no factors it is not prime or composite.

 Since 1 has only 1 factor it is not prime or composite.

 A multiple can be made by multiplying a number.  For examples: some multiples of 6 are 6, 12, 18, 24, 30, 36 etc because 1 x 6 = 6, 2 x 6 = 12, 3 x 6 = 18, 4 x 6 = 24, 5 x 6 = 30, 6 x 6 = 36, etc.

 When we multiply we can use the expanded multiplication algorithm.  See example below:

     2 5 4

   X      3

        1 2    (3 ones x 4 ones)

     1 5 0    (3 ones x 5 tens)

 + 6 0 0    (3 ones x 2 hundreds)

    7 6 2

 To practice multiplying.  

 To practice factors and multiples.

 To practice multiplication facts.    

 To practice multiples.

 To practice using a multiplication grid. 

 To practice multiplication facts.

Multiplication and Division Notes (doc file)

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