This elementary problem has made netizens worldwide stand out

How about you? Can you do it?

Recently, netizens are spreading a logical problem quite briefly. This problem is taken in the SASMO exam (Singapore & Asia International Mathematics) 2014 - a competition for elementary students. However, instead of being able to solve it easily, adults must have a headache to think and not solve it.

The problem is called: "Cheryl's birthday". Can you solve it? Let's try it.

Problem: Birthday of Cheryl (Vietnamese goods).

Albert and Bernard recently played with Cheryl, and both wanted to know her birthday. Cheryl instead of straightforward, gives a list of 10 days:

May 15, May 16, May 19

June 17, June 18

July 14, July 16

August 14, August 15, August 17

Cheryl then told Albert the month of birth, and said the date of birth for Bernerd.

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

Bernard : I didn't know at first, but now I know.

Albert: I know it now.

So what is Cheryl's birthday?

Think about it. The answer is right below.

Answer

To solve this problem, you must stick to the statements of Albert and Bernard, the list of days Cheryl offers.

Notice that the list is only available on the 18th and the 19th. If Cheryl's birthday on this 2 days, Bernard knew. But the truth is not that, so we eliminated on June 18 and May 19.

Next, Albert only knew the month, but he could confirm that Bernard did not know. So it can be inferred that Cheryl's birth month is not 5 or 6.

When this information is obtained, Bernard immediately guesses Cheryl's birthday. This proves that the birth date cannot be the 14th, because it is repeated in both July and August.

So, we only have 3 choices: July 16; August 15; August 17.

Time to last data. When Bernard figured out Cheryl's birthday, Albert figured it out too, so it proved Cheryl's birth month was July. The reason was because in August, Albert wouldn't be able to know the exact date of birth, because we have up to 2 days.

So in short, Cheryl's birthday is July 16 .