There is the common saying that “one man’s trash is another man’s treasure” to show that different things may have different value to different people.

However, I teach a class of students and often find myself explaining things of various difficulty to students. Sometimes something that is “obvious” or well known to one student may be completely new to another. So one students waste of time is an important learning experience for another.

I was wondering if you knew of any idioms or expressions for this specific situation in difference of knowledge in which I am trying to get across that just because it’s obvious to you doesn’t mean it won’t help another person?

  • Do you mean that the students have varying levels of prior experience, or that they have varying levels of aptitude for the subject?
    – alphabet
    Commented Jul 9 at 4:29
  • "The lucky ten thousand" is a helpful idea related to your situation, but it isn't a common idiom and isn't precisely what you are looking for. xkcd.com/1053
    – jejorda2
    Commented Jul 9 at 8:45
  • I guess you want something more polite than even a blind squirrel can find a nut once in a while.
    – Stuart F
    Commented Jul 9 at 8:56
  • Basically you need to teach the students that they can learn from each other as well as you.
    – Xanne
    Commented 2 days ago

1 Answer 1


In the context of teaching and learning, there’s a saying that captures this situation well:

“What’s old hat to one person may be a revelation to another.”

This idiom emphasizes that knowledge and familiarity vary among individuals, and what seems obvious to one can be valuable and enlightening to someone else. It’s a great reminder that everyone’s learning journey is unique!

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  • 1
    Is this a real adage? Can you provide reference please?
    – Gio
    Commented Jul 9 at 11:19
  • This information is very useful. Thank you for sharing. tellthebell
    – Marlene495
    Commented Jul 10 at 4:28

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