Difficulty Popularity

The host of a game show, offers the guest a choice of three doors. Behind one is a expensive car, but behind the other two are goats.

After you have chosen one door, he reveals one of the other two doors behind which is a goat (he wouldn't reveal a car).

Now he gives you the chance to switch to the other unrevealed door or stay at your initial choice. You will then get what is behind that door.

You cannot hear the goats from behind the doors, or in any way know which door has the prize.

Should you stay, or switch, or doesn't it matter ?

After you have chosen one door, he reveals one of the other two doors behind which is a goat (he wouldn't reveal a car).

Now he gives you the chance to switch to the other unrevealed door or stay at your initial choice. You will then get what is behind that door.

You cannot hear the goats from behind the doors, or in any way know which door has the prize.

Should you stay, or switch, or doesn't it matter ?

Difficulty Popularity

Difficulty Popularity

I have two hourglasses

A) Measures an exact 7 hours

B) Measures an exact 4 hours.

Using these two hour glasses, you need to measure an exact nine hours ?

A) Measures an exact 7 hours

B) Measures an exact 4 hours.

Using these two hour glasses, you need to measure an exact nine hours ?

Difficulty Popularity

In front of you, there are 9 coins. They all look absolutely identical, but one of the coins is fake. However, you know that the fake coin is lighter than the rest, and in front of you is a balance scale. What is the least number of weightings you can use to find the counterfeit coin?

Difficulty Popularity

Outside a room there are three light switches. One of switch is connected to a light bulb inside the room.

Each of the three switches can be either 'ON' or 'OFF'.

You are allowed to set each switch the way you want it and then enter the room(note: you can enter the room only once)

Your task is to then determine which switch controls the bulb ??

Each of the three switches can be either 'ON' or 'OFF'.

You are allowed to set each switch the way you want it and then enter the room(note: you can enter the room only once)

Your task is to then determine which switch controls the bulb ??

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