Thanks for your thorough and detailed answer, which has been helpful yet lead me to another question.
Fractions and decimals are 'countable'.
But linguistically, when we talk about count(able) nouns, the singular form of the noun means the form of a word used when talking or writing about one thing
: or denotes a unit quantity
Another quote from a dictionary : A language has grammatical number when its nouns are subdivided into classes according to the quantity they express, such that:
1)Every noun belongs to a single number class. (Number partitions nouns into disjoint classes.)
2)Noun modifiers (such as adjectives) and verbs have different forms for each number class, and must be inflected to match the number of the nouns they refer to. (Number is an agreement category.)
This makes me wonder, how can we count a countable noun in decimals or fractions? Shouldn't they be counted in integers?
Hence, one and a half hour, 1.75 kilometer, 0.5 degree, etc?
I might be wrong, and do partly agree with the contradicting opinions, but am still not totally convinced.