I don't agree with your reasoning, Eddie. On your logic, we would have to say *"One of the mangoes are ripe" on the gounds that "mangoes" is plural!Since the word "mangoes" is plural, the correct sentence would be "none of the mangoes are ripe."
I was taught in the UK, and I agree with you - "None are" just sounds more correct to me...Thanks, Onager!
I'm wondering if there's a regional preference of "is" over "are" or vice versa in conjunction with "none." I seem to have been taught exclusively "none are" (northeastern USA). Hmm...
I think a better rendering of the meaning of the sentence would be "Not one of the mangos is ripe." The fact is that if you restructure the sentence, you can force it to be either singular or plural. When I learned grammar a long time ago, I was taught that "none" is always singular and that the number of the object of a preposition (mangos) has no bearing on the number of the subject (none). I have since learned that a lot of learned people don't agree with that. Evidently, both options are considered standard usage, so I have betrayed my teachers and stopped making the argument for exclusive use of the singular.I also prefer "none are." (Northern California). The meaning of the sentence is "There are no ripe mangos," and I think the verb is conforming to that meaning. That's just my best guess.