Question of the Day: Two information theoreticians, Alice and Bob, perform a trick with a shuffled deck of cards, jokers removed. Alice asks a member of the audience to select five cards at random from the deck. The audience member passes the five cards to Alice, who examines them, and hands one back. Alice then arranges the remaining four cards in some way and places them face down, in a neat pile.
Bob, who has not witnessed these proceedings, then enters the room, looks only at the four cards, and correctly determines the missing fifth card, held by the audience member. How is this trick done? Try to come up with the simplest solution possible.
Note: The only communication between Alice and Bob is through the arrangement of the four cards. There is no encoded speech or hand signals or ESP, no bent or marked cards, no clue in the orientation of the pile of four cards (i.e. it would suffice for Bob to be read the list of the four cards in order.)
Logic - Prolog
factorial(0,1). factorial(N,F) :- N>0, N1 is N-1, factorial(N1,F1), F is N * F1.
A deductive argument is one in which the author intends the evidence to be so strong that it is impossible for the premises to be true and the conclusion false, or the conclusion follows necessarily from the premises.
An inductive argument is one in which the author intends the evidence only to be so strong that it is improbable that the premises could be true and the conclusion false, or the conclusion is likely true if the premises are true.
Most common example
Satisfiability - Conjunctive Normal Form