What is the next number in this matchsticks series riddle?

How can you leave a room with two legs and return with six legs?

There was a man he lives in a hotel each morning he presses the first floor button each evening if there is a person in the elevator he asks him to press the 10 floor button if there is no one in the elevator he takes the stairs why.

What is the word or phrase?

Transform the word THINK into BRAIN while changing only one letter at a time in a manner that each of the word in the process is a real word!!!

Can you find the next number in the below sequence
3 , 7 , 10 , 11 , 12 , 17 ?

Which five letter word can be added at the end of below word to form a
valid word?

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Before Mount Everest was discovered, what was the highest mountain in the world?

What does an Island and the letter T have in common?

A wealthy man lives alone in a small cottage. Being partially handicapped he had everything delivered to his cottage. The mailman was delivering a letter one Thursday when he noticed that the front door was ajar. Through the opening he could see the man's body lying in a pool of dried blood. When a police officer arrived he surveyed the scene. On the porch were two bottles of warm milk, Monday's newspaper, a catalog, flyers, and unopened mail. The police officer suspects it was foul play. Who does he suspect and why?