Brain Teasers - Light Bulb

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Intermediate
Difficulty
Rating

Problem Definition

Light Bulb

Situation:

You are standing in front of a room with one light bulb inside of it. You cannot see if it is on or off. Outside the room there are 3 switches in the off positions. You may turn the switches any way you want to. You can open the door and enter the room, but you cannot use a switch anymore afterwards

Question:

How can you determine which switch turns the light on and off?

Coins

Situation:

You have a pile of 24 coins. Twenty-three of these coins have the same weight, and one is heavier. Your task is to determine which coin is heavier and do so in the minimum number of weighings. You are given a beam balance (scale), which will compare the weight of any two sets of coins out of the total set of 24 coins.

Question:

How many weighings are required to identify the heavier coin?

Truth or Lie

Situation:

You are in a room with 2 doors leading out. Behind 1 door is a coffer overflowing with jewels and gold, along with an exit. Behind the other door is an enormous, hungry lion that will eat anyone opening the door.

You do not know which door leads to the treasure and exit, and which door leads to the lion. In the room you are in with 2 men. The first is a knight, who always tells the truth, and a knave, who always lies. Both of these individuals know what is behind each door. You do not know which individual is the knight, or which one is the knave.

Question:

You may ask one of the individuals exactly 1 question. What should you ask in order to be certain that you will open the door with the coffer behind it, instead of the hungry lion?

Dogs

Situation:

Two scruffy dogs were walking down the street. The first dog turned to the other and said, "Do you realize that if one of your fleas jumped onto me we would have the same number of fleas?" The second replied, "Yes, but if one of your fleas jumped onto me I would have five times as many fleas as you."

Question:

How many fleas are on each dog to begin with?

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4.8k
Times solved
Intermediate
Difficulty
Do you have questions on this case? Ask our community!