This puzzle is for Harry Potter fans. Do you know why Tom Riddle is called Lord Voldemort?

Until it is measured, not known. Yet how you miss it when it has gone. What is it?

Christina, Allison and Lena are 3 daughters of John a well-known Mathematician, When I asked John the age of their daughters. He replied "The current age of her daughters is prime. Also, the difference between their ages is also prime."

How old are the daughters?

John’s parents have three sons: Snap, Crackle, and what’s the name of the third son?

There are people and strange monkeys on this island, and you can not tell who is who (Edit: until you understand what they said - see below). They speak either only the truth or only lies.
Who are the following two guys?
A: B is a lying monkey. I am human.
B: A is telling the truth.

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

Mr Black, Mr Gray, and Mr White are fighting in a truel. They each get a gun and take turns shooting at each other until only one person is left. Mr Black, who hits his shot 1/3 of the time, gets to shoot first. Mr Gray, who hits his shot 2/3 of the time, gets to shoot next, assuming he is still alive. Mr White, who hits his shot all the time, shoots next, assuming he is also alive. The cycle repeats. If you are Mr Black, where should you shoot first for the highest chance of survival?

When we see 2 but call 10?

You have two buckets of 11 liters and 6 litres.
How can you measure exactly 8 litres?

A shepherd had 18 sheep, out of which, all but ten died.

Can you tell us how many sheep was he left with?