Tricky interview question: How long will it take a lily pad to cover a quarter of its pond?
An interview at a bulge bracket investment bank in Australia was all going well until the following happened...
The question
If there is a lily pad in a pond, and it doubles in size every minute and will completely cover the pond in one hour, how long will it take to cover a quarter the pond?
The candidate's reply
"I scratched my head and looked out the window, pretending to be in deep thought and trying to cover up the fact that I had no idea. I finally replied: 'errr, 15 minutes'."
How he would have responded in hindsight
"Wow, what a great question. Given that the pond will be covered in one hour and that it doubles in size every minute, at one minute prior to the hour the pond would be half covered. Continuing this line of thought, if we go back another one minute, the pond would be a quarter covered, so the answer is 58 minutes."
How would YOU have answered?
Use the comments box below to suggest a better response to the interview question above.
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