Which tank will fill first?

It comprises roots which nobody sees,
Much taller than those trees,
Up and up it goes,
Still it never grows?

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

If you had a pizza with crust thickness 'a' and radius 'z', what's the volume of the pizza?

A lion and its tamer are standing inside a cage that measures 1 unit in radius. Both of them can effortlessly run at the speed of 1 unit maximum.

1) Suppose the lion is hungry, will he be able to eat up the tamer?
2) If yes, how long can the tamer survive?

2, 3, 5, 9, 17, _ What is the next number in the sequence?

You walk into a room that contains a match, a kerosene lamp, a candle and a fireplace. What would you light first?

It is deaf, Dumb and Blind!!!

Still, always tells the truth. What is it?

What numbers should go on the bottom line?
3 6 9 15
8 2 10 12
11 8 19 27
19 10 29 39
? ? ? ?

A man lives on the fifteenth floor of an apartment building. Every morning he takes the elevator down to the lobby and leaves the building. In the evening, he gets into the elevator, and, if there is someone else in the elevator, or if it was raining that day, he goes back to his floor directly. Otherwise, he goes to the tenth floor and walks up five flights of stairs to his apartment. Can you explain why he does this?