How many 3-digit numbers can be formed by using the digits 1 to 9 if no digit is repeated?

Explanation

There will be as many. 3 digit numbers as there are permutation of 9 different digits.taken 3 at time
Therefore, the required 3 digit numbers.

``
= ^9 p_3=9 !/(9-3) !=9 !/6 !=9 xx 8 xx 7 xx 6 !/6 !=504
``