Originally posted by: AnonymouseUser
Nowhere does the statement state that their must not be a vowel behind an even number, just that there must be an odd number behind a vowel.
The only cards that need to be turned are A and 1.
If there is a vowel on one side, then there must be an odd number on the other side.
As long as paper has only 2 sides, if there is a vowel behind an even number, there is ALSO an even number behind a vowel, which violates the rule. Unless the OP stated "If a vowel is face-up, there must be an odd number on the other side", you have to consider both approaches.
And why do you think that 1 needs to be flipped?