Consider the set S of all integers between and including 1000 and 99999. Call two integers x and y in S to be in the same equivalence class if the digits appearing in x and y are the same. For example, if x=1010, y=1000 and z=1201, then x and y are in the same equivalence class, but y and z are not. Find the number of distinct equivalent classes that can be formed out of S.

(In reply to solution by Charlie)

Not sure  but does your method count, for example 10000 and 100?  One of those is out of range, as are similar examples.

Posted by Kenny M on 2021-06-22 16:50:47