How many three-digit numbers are there with no digit repeated
Given: the three-digit number is required without digit repetition
Assume we have three boxes; the first box can be filled with any one of the nine digits (0 not allowed at first place).
Therefore, possibilities are 9C1, the second box can be filled with any one of the nine digits available possibilities are 9C1, the third box can be filled with any one of the eight digits available possibilities are 8C1.
Hence, number of total outcomes possible are 9C1 × 9C1 × 8C1 = 9 × 9 × 8 = 648