Answer:
[tex]1680[/tex]
Step-by-step explanation:
we need a 4-digit number from the numbers [tex]2,3,4,5,6,7,8\ and\ 9[/tex] (without repetition ).
possible number at thousand place [tex]=8[/tex]
Possible numbers at hundred place[tex]=8-1=7[/tex]
Possible numbers at [tex]10^{th}[/tex] place [tex]=7-1=6[/tex]
possible number at unit place [tex]=6-1=5[/tex]
So total possible numbers
[tex]=8\times7\times6\times5\\=1680[/tex]
Other method :
We are taking [tex]4[/tex] numbers out of [tex]8[/tex] and here order matters so we will use permutation.
Total possible numbers [tex]=^8P_{4}[/tex]
[tex]\frac{8!}{(8-4)!}\\ =\frac{8!}{4!}\\ =8\times7\times6\times5\\=1680[/tex]
