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The JAT and the Sikh LI Infantry Regiment tussle
A civillian went to a defense area in which there were two infantry regiments: the JAT Regiment and the Sikh LI Regiment. The two clans have always an axe to grind against the other and one calls themseves to be much superiot to the other.

A guests asks one soldier from a regiment, ” Where is the Jat Regiment?’ This one. Who do you wanna meet? Subedar Prem Singh.
Oh he is in the next accross.
So you are not Jat’s?

No we are. But the next one also call themselves Jat’s. But we are the real one’s. Ha ha ha!

Well akin to this case imagine there is a truth tellers’ Regiment and the liars’ Regiment. In the truth tellers’ Regiment there are people who *always* tell the truth. In the liars’ Regiment there are people who *always* lie.
However both being part of the same Corps, interaction continues between the Regiments and it’s not uncommon to find a liar in the truth teller village, and vice versa (guess which Regiment is better off :-).

When you arrive on the cantonement, you see the two Regiments but you don’t know which is the truth tellers’ Regimentand which is the liars’ Regiment. You decide to go to one of the Regiment, turn to the first person you see and ask.

But…what question would you ask?

And you should also know that the people in these Regiments only answer ‘yes’ or ‘no’.

So what short and simple (no more than 4 words) question would help you know which village you are in?

You may Use all the problem solving tools to solve this problem!

- Posted on October 10th, 2006 in General, Puzzles | 3,853 Views |

1 Comment »

One Response to “JAT Regiment Versus Sikh Light Infantry”

1. Posted byPriyavrat on October 10th, 2006 at 2:19 pm

Most people try to solve this puzzle by guessing a question and then testing the different cases to see if it brings about the desired information.
We will, of course, take a different route to the solution. Formulating the question itself will be the last thing we’ll do.

We’ll start with the end result and work backwards to identify necessary conditions for the question. We’ll then infer the question from these conditions.

The end result is, of course, that we know which Regiment we’re visiting: Jat or Sikh LI.

One step before knowing which Regiment we’re in was to get a “Yes” or “No” answer.

But if we knew which Regiment we were visiting just by getting a “Yes” or “No” answer it would mean that we would have to construct the question is such a way that one response (”Yes”, for example) would be associated with the truth tellers’ Regiment (given only in that Regiment), and the other response (”No”, in this case) would be associated with the liars’ Regiment (again, given only in that Regiment).

Now, let’s suppose that we’re in the truth tellers’ Regiment.

If we happen to meet a Soldier from the Regiment (a truth teller) and ask our magic question, the answer must be “Yes”.

But if we happen to meet a liar in the truth tellers’ Regiment, the answer must also be “Yes”.

If both a liar and a truth teller provided the same response for the same question, it would mean that the question must relate to the soldier being asked. This is the only way the same question will be interpreted differently by different kinds of people.

Let’s now suppose that we meet a truth teller in the liars’ Regiment. We would ask the same magic question, but now we must get the answer, “No”.

This can happen only if the question is related to the ‘Regiment’. It is the only way the same question will be interpreted differently by the same person in different Regiment.

So we know the question relates to the Regiment and to the soldier.

Therefore, it is probably about the RELATIONSHIP between the soldierand the Regiment.

Now, equipped with all the information about the question, it’s time to try a question.

What about, “Is this your Regiment?”

Let’s see -

If we ask a truth teller in the truth tellers’ Regiment, we’d get a “Yes” answer. If we ask a liar in the truth tellers’ village, we’d also get a “Yes” answer. (because he’d lie). If we ask a truth teller in the liars’ village, we’d get a “No” answer. If we ask a liar in the liars’ village we’d also get a “No” answer (because he’d lie).

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