The number of natural numbers less than 1000 in which no two digits are repeated is

Number of single digit numbers  =  −→9   ( except 0)    Number of two digit numbers        =   −−→9×9=81    ( tenth place can be filled in 9 ways( except 0) and unit's place can be filled in 9ways   Number of three digit numbers     =   −−−→9×P2   9=648  ( hundred's placed can be filled in 9 ways ( except 0) and the remaining two                                                                                                        places can be filled with the remaining 9 numbers in P(9,2) ways.       The number of natural numbers less than 1000 in which no two digits are repeated is  =738