Multiplying by 5:

 

1)

Multiplying by 5:

A. This method will instruct you to write the answers from right to left.

1. When multiplying by 5, it is easier to divide by 2 and multiply by 10.

2. If the number you are multiplying is odd, then the last number will be a 5 (sce

Ex [2]), otherwise the last number is O.

B. Examples:

Ex [1] 5 x 142 = _

a) 142 / 2 = 71. Write 71.

b) Since 142 is even the last number is 0. Write 0.

c) The answer is 710.

Ex [2] 5 x 142857 =

a) 142857  / 2 = 71428 with a remainder of 1. Write 71428.

b) Since there is a remainder of 1, the last number is 5. Write 5.

c) The answer is 714285.

**Note: This trick works because 5- = 10 / 2.