A closed room contains three light bulbs (A, B, and C). Outside the room are three switches (1, 2, and 3). You switch Switch 1 ON for 10 minutes, turn it OFF, and turn Switch 2 ON. You immediately enter the room. Bulb A is lit, Bulb B is off but hot to the touch, and Bulb C is off and cold. Which switch controls which bulb?
Switch 1 controls Bulb B, Switch 2 controls Bulb A, and Switch 3 controls Bulb C.
Switch 2 is currently ON, so it lights Bulb A. Switch 1 was ON long enough to heat up Bulb B before being turned OFF. Switch 3 was never turned ON, leaving Bulb C unlit and cold.
About this riddle
Logic riddles give you a few facts and ask what must be true. List what you know, cross out what cannot be, and see what is left.
Difficulty: Hard. More like this: Logic riddles with answers or try Einstein's Logic Grid for a different kind of puzzle.
More logic riddles
The day before yesterday, Maya was 17 years old. Next year, she will turn 20. How is this logically possible?
You have 9 identical-looking coins, but 1 is counterfeit and slightly lighter than the others. Using a balance scale with two pans, what is the minimum number of weighings needed to guarantee finding the fake coin?
A shepherd needs to cross a river with a wolf, a goat, and a cabbage. His boat can carry only himself and one item at a time. If left unattended, the wolf will eat the goat, and the goat will eat the cabbage. How many one-way river crossings must the shepherd make to transport all three safely to the other side?
A rectangular field is twice as long as it is wide. If the perimeter of the field is 60 meters, what is the area of the field in square meters?
Five identical boxes are lined up in a row. A prize is hidden in one of them. Box A says 'The prize is in Box B or C.' Box B says 'The prize is in an even-numbered box.' Box C says 'The prize is in Box A.' Box D says 'The prize is in Box E.' Box E says 'The prize is not in this box.' Only the box containing the prize is telling the truth; all other boxes contain false statements. Which box holds the prize?
A line goes: eraser, ruler, eraser, ruler, eraser. What comes next?