What is the next number in this series?

4,12,84,3612....

What goes through cities and fields, but never moves?

If 1+9+8=1, what is 2+8+9?

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.

What will be the best approach to finding all the prime numbers less than 75 that leave an odd reminder when we divide them with 5?

What number do you get when you multiply all of the numbers on a telephone's number pad?

Can you start the fire using two pieces of wood?

John named his first son Alpha, second Beta, third Charlie and fourth Delta. What is the fifth son's name?

Replace all '*' with digits 1, 2, 3, 4, 5 and 6 to make below statement true.

* *
x *
=====
* * *

A man has eighty-one cows ( numbered 1,2,3...81 as such). The beauty is that cow no. 1 gives 1ltr of milk, cow no. 2 gives 2ltrs of milk and so on. The man wants to equally distribute the cows among his nine sons so that each one of them gets the same quantity of milk.