Brain Teasers & Mental Math
Roll a fair die repeatedly. What is the expected number of rolls to see all six faces at least once (the coupon collector problem)?
Model answer
E = 6 × (1/6 + 1/5 + 1/4 + 1/3 + 1/2 + 1/1) = 6 × (49/20) = 14.7 rolls. Each new…
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