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a mile away
Very easily. Always of something detected or observed. I can spot Paul from a mile away, just by the way he walks. After decades as an investigator, I can identify a con man a mile away.
If someone is miles away, they are completely unaware of what is happening or of what someone is saying, because they are thinking deeply about something else. Sorry, I was miles away. Could you repeat that? You didn't hear a word I said, did you? You were miles away.