Dr. Jones kept an antique clock in his office waiting room. One day after lunch he had only four patients. When he had returned from lunch the clock was still in the waiting room, but after the fourth patient left and Dr. Jones passed through the waiting room again, he noticed the clock was missing.

The police questioned the four afternoon patients, but they had gotten together and decided that every statement they would make would be a lie.

Adam said: None of us stole the clock. The clock was still there when I arrived.
Bert said: I arrived second. The clock was missing when I arrived.
Charlie said: I arrived third. The clock was still there when I left.
David said: The clock was missing when I arrived.

In what order did the patients arrive, and who stole Dr. Jones' clock?

I found it useful to let ABCD be the order in which each character made his appearance, etc. T is the order of appearance of the thief. We have directly from the characters statements:

T<A

T>=B

T<=C

T>=D

So

B,D <=T<=C   and T<A

This implies (BD) are some combination of (12), AC is a combination of (34). We also have from character statements that

B<>2 and C<>3, so the order is BDAC and T=D

Posted by FrankM on 2008-01-19 22:46:56