>>12204212We can only rule out A6 and B5, we can’t rule out A and B, that’s what I argued with some other people about. The statement would still be true if Albert had A2 or A3. When he says “I know you don’t know” all we can conclusively infer is that he knows Bernard doesn’t have 5 or 6, because from Bernard’s perspective, if he had a 5 or 6 he would immediately know the correct pad.
I think the answer is D4.
Here is my reasoning:
When Albert says “I know you don’t know the correct pad” that means he knows Bernard doesn’t have 5 or 6, because obviously if he did he would know the correct pad. Albert says “I don’t know the correct pad”, so from Alberts perspective: he knows it can’t be 5 or 6, but he still doesn’t know the correct pad.
Now let’s look at Bernard’s perspective: Albert knows it isn’t 5 or 6, but Albert still doesn’t know what the correct pad is. If Albert had B, then eliminating 5 and 6 would give him the correct pad, it would have to be B4. Since Albert said “I don’t know” then we can be sure Albert doesn’t have B.
AHA! Bernard says. I know my number, and I know you don’t have B, now I know the correct pad. Bernard’s number is 4, The correct pad is D4, and Bernard figures this out by eliminating the possibility that Albert has B. If he had any other number than 4, Alberts statement would leave too many remaining possible answers.
