1/6th cannot be expressed as a whole number because it is a fraction that represents a part of a whole. A whole number is an integer without fractions or decimals, such as 1, 2, 3, etc. Since 1/6th is less than 1, it does not equate to any whole number.
To understand this better, consider dividing a whole into six equal parts. Each part is 1/6th of the whole. Since none of these parts make up a complete whole, 1/6th remains a fraction and cannot be converted into a whole number.