Find the number of 7-digit (base-10) numbers, such that each of the digits 1,2,3,4,5 must appear in the number (once or more).
Clearly, no leading zeros.
(In reply to re: analytic solution, subject to error
by Steve Herman)
Just that a brute force approach would involve 10^7 numbers to be tested for the presence of numbers that had the given digits, requiring a lot of computer time, in any of the languages I use.
Pre-analysis for a more sophisticated computer approach would lead to these 8 cases anyway, so I figured, why not go straight for an analytic approach, rather than start an analysis for a program.
Posted by Charlie
on 2015-11-19 13:31:43