Input (grade 5): Here, the identity element is 1, since 1 × a = a × 1 = a for any rational number a. The inverse of a is 1/a, since a × 1/a = 1.
Output (grade 9): When the number is 1, then the 1 is not written because 1 times any number is that number (1 × y = y) and so is not needed.