Interview Question: One Lucky Dude

Sample Question #152 (probability brainteaser)

I give you a coin to toss. You toss it 100 times and get 100 heads. (Lucky you!) What’s the probability of getting heads again on your 101st toss?

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One Response to Interview Question: One Lucky Dude

  1. Brett says:

    This is an excellent question that tests your ability to go beyond the textbook.  The textbook answer would be 50%, since that’s the odds of getting heads on any toss.  But if you got 100 heads in a row, that’s something wrong with the coin, e.g., it’s a loaded coin, so it’s likely when you toss again you’ll get another head.  If you think like this, the answer is 100%.  The "ideal" answer would be to mention both solutions. (But, please do not try to give "ideal" answers at an interview! Just give your best answer. Nobody can be perfect.)

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