Final answer:
In the group of numbers 1/2, 4, 1.73, and 2, the number that does not belong is 1.73 because it is the only non-integer, as opposed to the others which can be either whole numbers or fractions of an integer.
Step-by-step explanation:
When identifying which number does not belong in the group consisting of 1/2, 4, 1.73, and 2, we need to consider various properties of these numbers. Looking at the group, we can first notice that 1/2 is a fraction, 4 is a whole number, 1.73 is a decimal, and 2 is also a whole number. However, to find the one that doesn't belong, we can compare some specific attributes.
One approach is to consider whether these numbers can be classified as integers or not. An integer is a whole number that can be positive, negative, or zero, and does not include any decimal or fractional parts. In the given group, 1.73 stands out because it is the only non-integer. All the other numbers (1/2, 4, and 2) can be expressed as integers or fractions thereof; 1/2 is a fraction that can be part of an integer when doubled, 4 is already an integer, and 2 is an integer. In contrast, 1.73 cannot be expressed as an exact fraction without an infinite decimal expansion, setting it apart from the rest.