Light Bulbs
There are 2 rooms. Each room contain 3 light bulbs as well as 3 switches that correspond to the light bulbs in the other room. How many times do you need to enter either of the rooms before you can accurately determine which switch corresponds to which light bulb?
Note: Your height is 2 inches (5 centimeters) less than the ceiling's height. This information is useful when solving this problem.
The answer is 3.
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1 solution
Go to the first room. Flip 2 of the switches, then close one of the switches after a short amount of time. Then go to the second room. You will know which switch the lit light bulb in connected to. After that, touch the 2 closed light bulb. The hot one correspond to the one you closed after a short amount of time. Repeat the step to flip the switches then go back to the first room and identify the light bulbs.
The last note in the problem is useful because it implies you are able to touch light bulbs on the sealing with your hand, or by jumping.