Luis Garavito killed Density x Volume.

Who is Luis Garavito ?

What comes
Once in a Year
Twice in a Month
4 times in a Week
6 times in a Day

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.

As you can see that fifteen matches have been used to form an arrangement. What you have to do is remove any six of them to make them ten.

Can you think of a smallest +ve number such that if we shuffle the digits of the number, the new number becomes double the original number?

If all Goats are Sheep and all Sheep are Deers, are all Deers Goats ?

Find the Next Number in the Sequence

2 9 3 1 8 4 3 6 5 7 ?

A high school has a strange principal. On the first day, he has his students perform an odd opening day ceremony:

There are one thousand lockers and one thousand students in the school. The principal asks the first student to go to every locker and open it. Then he has the second student go to every second locker and close it. The third goes to every third locker and, if it is closed, he opens it, and if it is open, he closes it. The fourth student does this to every fourth locker, and so on. After the process is completed with the thousandth student, how many lockers are open?

In 1990, a person is 15 years old. In 1995, that same person is 10 years old. How can this be?

What is the largest number you can write with just 3 digits?