Math CentralQuandaries & Queries


Question from Angel, a student:

I need to know all the 4 digit combinations starting with 7 and with no repetitions.


Since you are starting with a 7 you only have to choose 3 of the 4 digits. You can generate them all using the Combinatorial Object Server page that generates combinations, Choose all k-permutations, set n = 10 and k = 3. This will give you all permutations of 3 items chosen from {1, 2, 3, ..., 10}. Whenever you see a 10 just replace it by a 0 and you will have what you need.


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