Question

How many 4 digit numbers can be formed by using 1 to9 if repetition of digits is not allowed​

Answer 1

$\underline{\Huge\mathfrak{Answer-}}$

Given ;

• 9P4 = 9! / (9-4)!

=> 9! / 5!

=> 9 × 8 × 7 × 6 × 5! / 5!

=> 9 × 8 ×7 × 6

=> 3024