Comment
Share
Q)

# The total number of 4 digit numbers in which the digits are in descending order is ?

4 digits are selected from any of the 10 numbers $0,1,2,.....9$.
Since the numbers are arranged in descending order $0$
No. of selection of any 4 numbers from $0,1,2,....9 =^{10}C_4$
$\therefore$ The required no. of 4 digit numbers = $^{10}C_4$