Given: We have 10 numbers i.e. 0,1,2,3,4,5,6,7,8,9

To Find: Number of 3-digit numbers formed with no repetition of digits.

Conditions: No digit is repeated

Let us represent the 3-digit number

First place can be filled with 9 numbers, i.e. 1,2,3,4,5,6,7,8,9 (0 cannot be placed as it will make it a 2-digit number) = 9 ways

Second place can be filled with remaining 9 numbers (as one number is used already) = 9 ways

Similarly, third place can be filled with 8 numbers = 8 ways

Total number of 3-digit numbers which can be formed

= 9 × 9 × 8= 648