Is the answer 27/256?

If not, what is?

I think the answer was 1/3

jscoligan wrote:Is the answer 27/256?

If not, what is?

Four envelopes
[] [] [] []
y x x x

1/4 2/3 1/2 1/1

For the second one 2 wrong ones from 3 right ones can be picked
For the third one 1 wrong one from remaining 2 right ones can be picked
For the fourth one 1 wrong one only is left. so 1/1

there can be 4 different ways of attaining a y.
therefore, 4*(1/4)(2/3)(1/2)(1/1) = 1/3

I hope this is correct..