in a guidebook on Italy, you find 10 cities you wish to visit, but only have time on your upcoming trip to visit 7. How many unique itineraries are possible for you to choose ?

Question

directrix · Answer

You have 10 choices for the first stop on the trip, then 9 choices for the second stop. Continue in that manner until you have the number of choices for the seventh (last) stop on the itinerary.

Then use the Fundamental Principle of Counting to get the number of unique itineraries.

directrix · Answer

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