Exercise 1.3

Fred is planning to go out to dinner each night of a certain week, Monday through Friday, with each dinner being at one of his ten favourite restaurants.

(a)
How many possibilities are there for Fred’s schedule of dinners for that Monday through Friday, if Fred is not willing to eat at the same restaurant more than once?
(b)
How many possibilities are there for Fred’s schedule of dinners for that Monday through Friday, if Fred is willing to eat at the same restaurant more than once, but is not willing to eat at the same place twice in a row (or more)?

Answers

(a)
Fred has 10 choices for Monday, 9 choices for Tuesday, 8 choices for Wednesday, 7 choices for Thursday and 6 choices for Friday.

10 × 9 × 8 × 7 × 6

(b)
For the first restaurant, Fred has 10 choices. For all subsequent days, Fred has 9 choices since the only restriction is that he doesn’t want to eat at the restaurant, he ate at the previous day.

10 × 94

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2021-12-05 00:00
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