7-digits numbers with digits 1, 3, 4, 6, 7, 8,9 each once
Source: 2020 Austrian Regional Competition For Advanced Students p2
November 22, 2020
Digitsnumber theory
Problem Statement
The set consists of all -digit positive integer numbers that contain (in decimal notation) each of the digits and exactly once.
(a) Find the smallest positive difference of two numbers from .
(b) How many pairs with and from M are there for which ?(Gerhard Kirchner)