Let be the set of all seven-digit numbers that can be formed using the digits 0, 1 and 2
MATHEMATICS · Subjective · CBSE · Mathematics · Permutations and Combinations · Permutations and Combinations
Problem
Let S be the set of all seven-digit numbers that can be formed using the digits 0, 1 and 2. For example, 2210222 is in S, but 0210222 is NOT in S. Then the number of elements x in S such that at least one of the digits 0 and 1 appears exactly twice in x, is equal to ____.