Albert knows the month bernard day. Difficult school task has become an Internet hit

09.04.2019

A new Internet virus drew the attention of Mashable.

In four days, Kong's post was shared by over 5,000 Facebook users. Interneters were excited by the complexity of the task, as well as the TV presenter's remark that it was designed for fifth-graders.

The condition of the task is as follows.

"Albert and Bernard just met Cheryl and wanted to know when her birthday was. Cheryl gave them a list of ten possible dates:

Cheryl then told Albert what month she was born, and Bernard what date. After that, the following conversation took place between the men.

I don't know when Cheryl's birthday is, but I know Bernard doesn't know that either," Albert stated.

At first I didn't know when Cheryl's birthday was, but now I know,” Bernard replied.

And now I know when Cheryl was born, - said Albert.

So when is Cheryl's birthday?"

The entry on Kenneth Kong's page garnered over 1,500 comments and was widely shared on other blogs as well as in the media. Many participants in the discussion admitted that they felt too stupid for not being able to solve a problem intended for fifth grade students.

However, as it turned out two days later, the problem turned out to be not an ordinary school one, but an Olympiad one. In addition, it was designed for 14-year-old students. This was reported to Kong by representatives of the SASMO organization (Singapore and Asean Schools Math Olympiads). The TV presenter himself admitted that he even quarreled with his wife over the discussion of this task.

Later, a solution to the task appeared in the Study Room organization community.

“First, we need to find out if Albert knows the month or the day. If he knows the day, then there is no chance that Bernard knows Cheryl's date of birth. So Albert knows the month.

We know from the first line that Albert is sure that Bernard does not know his date of birth. Therefore, May and June can be excluded, since the 19th is only present in May (among the dates listed), and the 18th is only in June.

So Bernard knows that May and June can be excluded.

After that, Bernard can find out the month when Cheryl was born. The remaining dates are July 16, as well as August 15 and August 17. At the same time, July 14 and August 14 can be excluded, since if Cheryl told Bernard that her birthday was on the 14th, then Albert would not be able to give an exact answer about the full date.

Subsequently, Albert stated that he, like Bernard, knows Cheryl's date of birth, then he knows that she was born in July. If it were August (recall that Albert had data on the month), then he could not say for sure whether the birthday falls on August 15 or 17.

On April 11, Singaporean TV presenter Kenneth Kong posted a logic puzzle for schoolchildren on his Facebook. In two days, social network users shared it more than 4,400 times and had a serious debate in the comments. Mashable drew attention to the story.

Kenneth's first entry reported, that the problem was rated P5 - suitable for 10-year-olds, but it turned out to be so difficult that he even quarreled with his wife about finding a solution. At the time of the publication of the picture, he himself did not know the answer, since the niece of his friend showed him the problem.

A task

Albert and Bernard have just met Cheryl. They want to know when her birthday is. Cheryl gave them ten possible dates: May 15, May 16, May 19, June 17, June 18, July 14, July 16, August 14, August 15, and August 17. Cheryl then told Albert the month of her birth and Bernard the day. After that, a dialogue took place.

Albert: I don't know when Cheryl's birthday is, but I know Bernard doesn't know either.

Bernard: At first I didn't know when Cheryl's birthday was, but now I know.

Albert: Now I also know when Cheryl's birthday is.

When is Cheryl's birthday?

Two days later, when the challenge went viral online, Kenneth was contacted by SASMO (Singapore and Asean Schools Math Olympiads - Math Olympiads for Singapore and ASEAN countries) and sent him a reply, specifying that it was actually intended for children from 14 years (level Sec 3).

According to representatives of SASMO, in their ten years of practice, Olympiad tasks have never hit the net, because children are forbidden to use mobile phones during their execution. Nevertheless, they decided to clarify the situation so that parents of P5 children would not sound the alarm due to the fact that their child is not able to solve a puzzle that has spread through the network.

Solution

There are only 10 dates, and the days are in the range from 14 to 19. At the same time, only the 18th and 19th occur once. If Cheryl's birthday is the 18th or 19th, then Bernard would have been able to tell the month right away.

But how does Albert know that Bernard doesn't know the answer? If Cheryl told Albert that she was born in May or June, then her birthday could be May 19 or June 18. In this scenario, Bernard might know when Cheryl's birthday is. The fact that Albert knows for sure that Bernard does not know the answer suggests that May and June can be ruled out, and Cheryl was born either in July or August.

Initially, Bernard didn't know when Cheryl's birthday was. How did he know the answer after Albert's remark? Of the remaining five dates in July and August, ranging from 15 to 17, only 14 occurs twice. If Cheryl had told Bernard that her birthday was the 14th, then Bernard, after Albert's guess, still couldn't give an exact answer. The fact that he immediately understood everything suggests that Cheryl was not born on the 14th. Three possible dates remain: July 16, August 15 and August 17.

After Bernard spoke, Albert found out when Cheryl's birthday was. If she told him that she was born in August, Albert would not know the exact answer, because of the three remaining dates, two are in August. So Cheryl was born on July 16th.

Birthday

Albert and Bernard have just met Cheryl. They want to know when her birthday is. Cheryl gave them ten possible dates: May 15, May 16, May 19, June 17, June 18, July 14, July 16, August 14, August 15, and August 17. Cheryl then told Albert the month of her birth and Bernard the day. This was followed by a dialogue:

Albert: I don't know when Cheryl's birthday is, but I know Bernard doesn't know either.
Bernard: At first I didn't know when Cheryl's birthday was, but now I know.
Albert: Now I also know when Cheryl's birthday is.

When is Cheryl's birthday?

Answer: There are only 10 dates, and the days are in the range from 14 to 19. At the same time, only the 18th and 19th occur once. If Cheryl's birthday is the 18th or 19th, then Bernard would have been able to tell the month right away.

But how does Albert know that Bernard doesn't know the answer? If Cheryl told Albert she was born in May or June, then her birthday could be May 19 or June 18. In this scenario, Bernard might know when Cheryl's birthday is. The fact that Albert knows for sure that Bernard does not know the answer suggests that May and June can be ruled out, and Cheryl was born either in July or August.

Initially, Bernard didn't know when Cheryl's birthday was. How did he know the answer after Albert's remark? Of the remaining five dates in July and August, ranging from 15 to 17, only 14 occurs twice. If Cheryl had told Bernard that her birthday was the 14th, then Bernard, after Albert's guess, still couldn't give an accurate answer. The fact that he immediately understood everything suggests that Cheryl was not born on the 14th. Three possible dates remain: July 16, August 15 and August 17.

After Bernard spoke, Albert found out when Sherip's birthday was. If she told him that she was born in August, Albert would not know the exact answer, because of the three remaining dates, two are in August. So Sherip was born on July 16th.

double chess

Two people play chess according to the following rules: first, white makes two moves, then two black moves, then again two white moves, and so on.
If one of the kings is in check (say, black), then in this case the move immediately goes to black, but they have the right to only one move to get away from the check (if it is impossible to leave in one move, then, as usual, checkmate .)
Task: to prove that in such a game White is guaranteed at least a draw with the best play.

Answer: If at the best game if white had a strategy for black, in which white loses, then white could first move the knight and return it to the initial position (so that the position does not change). Now Black finds himself in a situation identical to White's original position up to mirror symmetry. That is, White, using a mirror analogue of Black's winning strategy, can win. It turns out a contradiction. So White is guaranteed at least a draw.

MPs

In one parliament, the deputies were divided into conservatives and liberals. Conservatives only told the truth on even numbers, and on odd numbers they only told lies. Liberals, on the other hand, only told the truth on odd numbers, and on even numbers they only told lies. How, with the help of one question posed to any deputy, it is possible to determine exactly what date is today: even or odd? Answers must be definite: "yes" or "no".

Answer: It is necessary to ask any deputy: "Are you a conservative?" If he answered “yes”, then today is an even number, and if “no”, then it is odd. On even numbers, conservatives will say a true yes, and liberals, lying, will also say yes. On odd numbers, on the other hand, conservatives answering a question will say no, but liberals, who speak only the truth these days, will also say no.

What day is it?

Alex only tells the truth one day a week. What day is it if the following is known:
1. He once said - "I lie on Mondays and Tuesdays"
2. The next day he said - "Today or Thursday or Saturday or Sunday"
3. The next day he said - "I lie on Wednesdays and Fridays"

Answer: Alex tells the truth on Tuesdays. And the first statement was made on Sunday

Project approval procedure

The company has three workshops - A, B, C, which have agreed on the procedure for approving projects, namely:

1. If shop B does not participate in the approval of the project, then shop A does not participate in this approval either.
2. If shop B participates in the approval of the project, then shops A and C take part in it.

Under these conditions, is Shop C required to take part in project approval when Shop A is involved in the approval?

Answer: The first statement can be reformulated as follows: if shop A participates in the approval, then shop B must also participate. Then, according to the second statement, shop C should take part in project approval.

On April 11, Singaporean TV presenter Kenneth Kong posted a logic puzzle for schoolchildren on his Facebook page. In two days, social network users shared it more than 4,400 times and had a serious debate in the comments.

In Kenneth's first post, the problem was rated P5, suitable for 10-year-olds, but it was so hard that he even got into a fight with his wife about finding a solution. At the time of the publication of the picture, he himself did not know the answer, since the niece of his friend showed him the problem.

Task text:

Albert and Bernard have just met Cheryl. They want to know when her birthday is. Cheryl gave them ten possible dates: May 15, May 16, May 19, June 17, June 18, July 14, July 16, August 14, August 15, and August 17. Cheryl then told Albert the month of her birth and Bernard the day. After that, a dialogue took place.

Albert: I don't know when Cheryl's birthday is, but I know Bernard doesn't know either.
Bernard: At first I didn't know when Cheryl's birthday was, but now I know.
Albert: Now I also know when Cheryl's birthday is.

When is Cheryl's birthday?

According to SASMO representatives, in their ten years of practice, Olympiad tasks have never hit the net, because children are forbidden to use mobile phones during their execution. Nevertheless, they decided to clarify the situation so that parents of P5 children would not sound the alarm due to the fact that their child is not able to solve a puzzle that has spread through the network.

The solution of the problem:

There are only 10 dates, and the days are in the range from 14 to 19. At the same time, only the 18th and 19th occur once. If Cheryl's birthday is the 18th or 19th, then Bernard would have been able to tell the month right away.

But how does Albert know that Bernard doesn't know the answer? If Cheryl told Albert that she was born in May or June, then her birthday could be May 19 or June 18. In this scenario, Bernard might know when Cheryl's birthday is. The fact that Albert knows for sure that Bernard does not know the answer suggests that May and June can be ruled out, and Cheryl was born either in July or August.

Initially, Bernard didn't know when Cheryl's birthday was. How did he know the answer after Albert's remark? Of the remaining five dates in July and August, ranging from 15 to 17, only 14 occurs twice. If Cheryl had told Bernard that her birthday was the 14th, then Bernard, after Albert's guess, still couldn't give an exact answer. The fact that he immediately understood everything suggests that Cheryl was not born on the 14th. Three possible dates remain: July 16, August 15 and August 17.

After Bernard spoke, Albert found out when Cheryl's birthday was. If she told him that she was born in August, Albert would not know the exact answer, because of the three remaining dates, two are in August. So Cheryl was born on July 16th.

After the dress incident at the end of February, which divided netizens into two warring camps, content that causes controversy between users is increasingly gaining popularity on the Internet. Many commentators on Kong's page have posted lengthy calculations and calculations, but have managed to come up with the wrong answer. About half of them claimed that Cheryl was born on August 17, but there were other options.

Gained extraordinary popularity on the web mathematical problem, which was published on his Facebook page by Singaporean TV presenter Kenneth Kong. A new Internet virus drew the attention of Mashable.

For four days record Kong has been shared by over five thousand Facebook users. Interneters were excited by the complexity of the task, as well as the TV presenter's remark that it was designed for fifth-graders.

The condition of the task is as follows.

"Albert and Bernard just met Cheryl and wanted to know when her birthday was. Cheryl gave them a list of ten possible dates:

Cheryl then told Albert what month she was born, and Bernard what date. After that, the following conversation took place between the men.

"I don't know when Cheryl's birthday is, but I know Bernard doesn't know that either," Albert stated.

"At first I didn't know when Cheryl's birthday was, but now I do," Bernard replied.

“And now I know when Cheryl was born,” Albert said.

So when is Cheryl's birthday?"

Later in the Study Room community appeared task solution.

“First, we need to find out if Albert knows the month or the day. If he knows the day, then there is no chance that Bernard knows Cheryl's date of birth. So Albert knows the month.

So Bernard knows that May and June can be excluded.