When the number is 1 , then the 1 is not written because 1 times any number is that number ( 1 Ã -- y = y ) and so is not needed . Here , the identity element is 1 , since 1 Ã -- a = a Ã -- 1 = a for any rational number a. The inverse of a is 1\/a , since a Ã -- 1\/a = 1 .