13 decks of cards have been mixed. What is the minimum number of cards that must be taken out from the above-mixed cards to guarantee at least one 'four of a kind?

What's the only room from which no one can enter or leave

Why do people go to bed?

One day Jenifer meets the Lion and the Tiger in the Forest of Forgetfulness. She knows that the Lion lies on Mondays, Tuesdays, and Wednesdays, and tells the truth on the other days of the week. The Tiger, on the other hand, lies on Thursdays, Fridays, and Saturdays, but tells the truth on the other days of the week. Now they make the following statements to Jenifer:

Lion: Yesterday was one of my lying days.

Tiger: Yesterday was one of my lying days too.

What day is it?

A king sentenced a man to the death sentence for some crime he had committed. Known for his kindness, the king told the culprit that he had a choice to die in a way he decides.

The culprit was clever and said something that saved him from death. What method do you think he must have chosen for his death?

In the image below, can you find the value of an angle(y)

In the addition below, all digits have been replaced by letters. Equal letters represent equal digits and different letters represent different digits.
ABCABA
BBDCAA
ABEABB
ABDBAA
------- +
AAFGBDH
What does the complete addition look like in digits?

What is the word or phrase below?
R | E | A | D

Which is the smallest number that you can write using all the vowels exactly once?

A Scientist was fifty years old in the year 2000 but he was forty years old in the year 2010. How can this be possible?

PS: It has a logical answer.