Given: Digits which can be used to make numbers are 1, 2, 3, 4, 5, 6, 7, 8 and 9

The number of these digits are 9

To find: total number of three-digit numbers with no digit repeated

Formula used:

Number of arrangements of n things taken r at a time = P(n, r)

∴ The total number of ways

= the number of arrangements of 9 things taken 3 at a time

= P(9, 3)

= 9 × 8 × 7

= 504

Hence, total number of three-digit numbers using digits 1 to 9 with no digit repeated are 504