Can someone explain this to me : \" Ask the leftmost person whether letters corr
ID: 3687272 • Letter: C
Question
Can someone explain this to me : "Ask the leftmost person whether letters corresponding to the other two appear in alphabetical order. Then, regardless of the answer, you will have one position which excludes a random person." Why is that the case?
You are on an island populated by three tribes. Members of one tribe always tell the truth. Members of the second tribe choose to tell the truth or lie, completely at random. Members of the third tribe consistently lie Tribe members can recognize one another, but you can't tell them apart. Three people from the island, one representing each tribe, come to visit. How can you identify who is from which tribe by asking only three yes/no questions? Each question must be directed at only one person, but you can ask the same person multiple questions. Hint: There are 6 possibilities for P1, P2, P3: LRT, LTR, RLT, RTL, TLR, TRL P1 P2 P3 Additional hint: Ask the leftmost person whether letters corresponding to the other two appear in alphabetical order. Then, regardless of the answer, you will have one position which excludes a random person.Explanation / Answer
Let T = Truth tellers R = Either Truth or Lie tellers at random L = pure lie tellers (fit to be lawyers!! as lawyers are liars most of the time!! as long as they can get away with dishonesty charges from the police!) P1 = Person 1 P2 = Person 2 P3 = Person 3 Assumed no 2 persons from the same tribe will visit us – every person will be from a different tribe! (Like a national ambassadors or high commissioners! visiting their union territory in a foreign nation!!) It is easier to split and tackle 2 person at a time: let us handle P1 and P2 You can try asking the person 1: “If I ask the second person whether he is truth teller or liar, what would he say”? case 1: P1 = L, P2 = T In case if the P1 is a liar, then P2 = T or R if P2 = T then P2 would say T but as P1 = L, P1 would say L case 2: P1 = T, p2 = t consider the other combinations: if P1 = T, then P2 = T or R if P2 = T, then P2 would say T hence P1 will also say T case 3: p1 = L, p2 = L p1 says t case 4: p1 = t, p2 = L p1 says L the 4 case outputs: L, T, T, L now ask the similar question to P1 about P3 instead of P2 and explore the 4 similar cases as illustrated below: let us handle P1 and P3 You can try asking the person 1: “If I ask the third person (=P3) whether he is truth teller or liar, what would he say”? case 1: P1 = L, P3 = T In case if the P1 is a liar, then P3 = T or R if P3 = T then P3 would say T but as P1 = L, P1 would say L case 2: P1 = T, P3 = t consider the other combinations: if P1 = T, then P3 = T or R if P3 = T, then P3 would say T hence P1 will also say T case 3: p1 = L, P3 = L p1 says t case 4: p1 = t, P3 = L p1 says L the 4 case outputs: L, T, T, L let us consider the hint given in the question: the hint says that Can someone explain this to me : "Ask the leftmost person whether letters corresponding to the other two appear in alphabetical order. Then, regardless of the answer, you will have one position which excludes a random person." Why is that the case? this is because left most person = P1 corresponding letters from 3 persons are: P1,P2,P3: LRT,LTR, RLT, RTL, TLR, TRL P1: LRT: LRT,LTR, P2: RTL: RLT, RTL, P3: TRL : TLR, TRL Ask P1 whether the letters for P2 and P3 appear in alphabetical order? which means: the letters of P2 are = RTL: RLT, RTL, in fact how do they appear? not in alphabetical order as L is before R in alphabet a to z letters of P3: TRL : TLR, TRL not in alphabetical order because T must be after R in a to z now we got it because the answer can be either yes or no only, If the P1 says Yes then it means that P1 is a Truth teller If the P1 says No then it means that P1 is a Liar hence we have excluded P1 as a random person now as I have explained with the 2 person tactics, we can pin point P2 and P3