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.
You have two bottles of pills marked with labels A and B. The pills are identical. The doctor has asked you to take one A pill and one B pill daily. You cant take more or less than that.
While taking out the pills one day, you took out one pill from A and by mistake took out two from B. You have no idea which pill is which now.
You cant throw away the expensive pills. What will you do now?
There are 20 people in an empty, square room. Each person has full sight of the entire room and everyone in it without turning his head or body, or moving in any way (other than the eyes). Where can you place an apple so that all but one person can see it?
The chance of Mr John winning the lottery is 10%. All participants lined up and Mr John is 4th in the row. The first three participants lose the lottery.
We have shown you a regular water barrel as below. Without using any measuring device can you check if the barrel is more than half-filled or less than half-filled?
