Name one eight-letter word with 'kst' in the middle, 'in' the beginning, 'and' at the end.?

You want to boil a two-minute egg. If you only have a three-minute timer (hourglass), a four-minute timer and a five-minute timer, how can you boil the egg for only two minutes?

A girl has as many brothers as sisters, but each brother has only half as many brothers as sisters. How many brothers and sisters are there in the family?

Prove that twice of ten is the same as twice of eleven.

How many people must be gathered together in a room, before you can be certain that there is a greater than 50/50 chance that at least two of them have the same birthday?

You have a roll of cloth 1km long. You have a machine which cuts this roll into pieces of 10-meter-long cloth.

How long would it take for the machine to cut the roll if each cut took 4 secs?

10+10 and 11+11 can give you the same answer.

Explain how?

What is the riddle which can be asked all day with a different correct answer each time.

There was an aeroplane crash, every single person died, but two people survived. How is this possible?

What four weights can be used to balance from 1 to 30 pounds?