Number of four digit numbers that can be formed using all the digits except zero such that every number has exactly 2 distinct digits in it is

Step-by-step solution

Two distinct digits can be choosen out of 9 digits is in ^9 C ₂=36 ways now we can form 2^4 different 4 digit numbers from which wecan excludethe two cases aligned & 36 (2^4-2 )=36 (16-2) & 504 aligned