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five pills |
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Suppose
you are taking one each of 5 different types of pills every day but you don’t
like having to open and close 5 different bottles, so at the beginning of each
(30-day) month you put 30 of each type of pill into one big bottle. When it is
time to take your pills, you draw them out of the big bottle one at a time until
you have (at least) one of each type. On the last day of the month you will draw
exactly 5 pills and they will all be different (because that’s all that’s
left in the bottle), but on other days you will generally have to draw more than
5 pills in order to have (at least) one of each type. So, the question is: On
the first day of each month (when there are 150 pills in the bottle), how many
pills, on average, must you draw from the bottle in order to have (at least) one
of each? Answer : Solutions (listed by author) |
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Copyright © 2000-2008 Michael A. Gottlieb & Ralph Leighton. All rights reserved.
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