What always comes into a house through the keyhole?

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

My location can be determined by the below rebus.
So where am i ?

Write the next letter in this sequence.
O, T, T, F, F, S, S, E, __
**Hint: It is a Number Series Puzzle

Give it food and it will live; give it water and it will die.

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?

What brings you down but never up?

Which tank will fill first?

With the help clues provided in the image, can you find the 5 digit key?

A Monkey, a squirrel, and an Eagle are racing to the top of the mango tree. Assuming all these animals are in perfect shape, Which animal will reach to Banana first?