"The party favor: puzzle, over which interesting poraskinut brains

The website offers the reader a logical puzzle, is published in August 2015. You need to respond immediately to two questions.

Thebusinesswomanmedia.soma Nadine is having a party, and she plans to invite three friends — arena, Doug and Moira. That said her friends before heading out to party:

Two days before the party: Eren: Doug is going to a party.

Doug: Moira won't come to the party.

Moira: Eren goes to a party only if I'm going too.

The day before the party: Eren: Moira coming to the party just in case if I will not do it.

Doug: even the number of people of the three of us will come to the party.

Moira: Eren coming to the party.

The day of the party: Eren: 2018 has not yet arrived.

Doug: Eren coming to the party just in case if I will come too.

Moira: at least one of us will come to the party.

Nadine also knows that all three of them — Eren, Doug and Moira:

  • Only one person never lies.
  • Only one (but not the one that is not lying, never lying in the day of the month, which can be divided into 2, and on other days tells the truth.
  • The remaining person is lying only in the numbers of the month, which can be divided into 3, and on other days tells the truth.
— Can you answer any of them coming to the party?— Can you identify the day, month and year will host the party, on the basis that it will be in the future?

Confused? Answer below!



Who of them will come to the party:

The first step to unlocking the understanding that none of the invited can't lie, two days in a row.

If the first statement Moira is incorrect, then each of the invited friends will be present at the party, and the first two claims Doug is incorrect and can not be. Therefore, the third statement Moira is loyal, and at least one person not coming to the party.

If the second statement Doug is wrong, it means (from the above) that only one person will come to the party. In order to be true, the first and third Moira's statement must be incorrect — which is impossible, since in this case, Doug lied to for two days. Therefore, the second statement is true Doug, and even the number of people coming to the party.

If Doug's not coming to the party, then the first statement arena is incorrect, and so the second assertion arena must also be true. This leads to the fact that the party will be an odd number of people, but we have already proved that the number will still be even. Then Doug will come to the party.

Since an even number of people will attend the party, one, Eren, or Moira, not coming to the party that makes the first statement Moira wrong. Therefore, the second assertion Moira is loyal, and Eren will come to the party, while Moira — no. The party will come Doug and Eren.

How to find the date of the party:

Having dealt with the question of who is invited is destined to come to the party, we know that the wrong statement is the first statement from Moira, and the third statement arena is potentially incorrect.

If all three days occur in the same month, or the second or both the first and the third day is an even day of the month, but in this case, none of the invited will not be able to lie. Consequently, either the second or third day is the first day of the month.

If the day prior to the party, is the first day of the month, then the day of the party falls on the second day of the month; Eren should be the person who is lying on even days of the month. Therefore, if Moira, not Eren lied on the first day, the number of the day must be divisible by 3. But none of the last day of the month is not divisible by 3. So, the day before the party is not the first day of the month, which means that the day of the party must be the first day of the month.

What makes the day before the party the last day of the month, and since no one, as we have seen, this day is not lying, that day may not be even.

This means that the number two days before the party even, but it also must not be divisible by 3 otherwise this day would have to lie to two people. Thus, the day two days before the party should be on 28 February of a leap is the only eligible option.

Because no one lies on the first day of the month the first statement arena is true, and 2018 has not yet arrived.

Finally, as the only non-leap year 2018 is 2016, we may conclude that the party was held on March 1, 2016.

via mixstuff.ru/archives/113567