Hi Jasmin,

This is indeed an interesting question which is probably relevant for quite a lot of users, so I am happy to provide my perspective on it:

• First of all, it is very unlikely that you this information is up to date. Almost no consulting company uses brain teasers anymore - for obvious reasons.
• Still, given your question, you may think of any possibility to measure the light being on from either inside or outside of the refrigerator. Below you may find some examples:
  • From the inside: Use some type of photochemical paper that reacts to the light inside of the refrigerator, put a smartphone inside the refrigerator with a timer/ live stream of the inside, measure the heat/ electrical voltage of the light, sit inside the refrigerator (note: please do not actually do this)
  • From the outside: Put a hole in the door (though this might destroy the refrigerator)

In case you want a more detailed discussion on how to best approach any type of case study question, please feel free to contact me directly.

I hope this helps,

Hagen

Hello!

That is a variant of the 3 bulbs problem! It´s about seeing if it got warm. 

however, these type of brainteasers are extremly weird in consulting tbh, and I wouldn´t worry about them at all anymore. 

Hope it helps!

Cheers, 

Clara

No respectable company will do a case like that nowaways. I hadn't heard of brain teasers in consulting interviews in 20 years…

Honestly, there's no good answer to a bad question.

But well, I guess you can make a hole in the door, put a camera inside the fridge, you can also get inside the fridge (not a good idea). But if the objective is know if the light is turning on after you close the door, you can simply open the door and touch the light bulb - the temperature will be higher if it was on for a long time.

(editiert)