- One and a half hours are allowed for the exam.
- An hour and a half is allowed for the exam.
My question is that why those two sentences read differently when it comes to verb being singular or plural. Please explain. I can't really understand the double standard in the examples. The same verb with the same idea but in two different forms. Why?
An hour and a half = a recognised name for one period of time lasting 90 minutes, so that one period is treated as the singular.
I can't actually give you a logical explanation as to why this is though, unfortunately, but in BrE at least, that's just how it is.