twenty-twenty

[light]

hello,
when we want to say something is perfect we use something like "ohh, it is four out of four" in my mother thongue (don't know exactly why-guess it has got something to do with music notes)

is the english equivalent "twenty-twenty"?
can we say "oh it is twenty-twenty"?
and what is the story behind the number twenty?

thanks in advance

[susiedqq]

20/20 is perfect eyesight; to have a perfect perception of something is to have 20/20 on it.

Another expression is "hindsight is 20/20/" That means to look back on the (past) situation now, you can see it perfectly.

I never should have bought that car.
Well, hindsight is 20/20. You didn't know then that it had been in a wreck.