Question

Form $2$ digit number using $0,1,2,3,4,5$ without repeating the digits. Write the sample space $S$, number of sample points $n\left(S\right),U,n\left(U\right)$ for $U$ is the event that the number so formed is divisible by $5$.

Answer 1

The sample space is
$S=\{10,12,13,14,15,20,21,23,24,25,30,31,32,34,35,40,41,42,43,45,50,51,52,53,54\}$
$\therefore n\left(S\right)=25$
Now $U$ is event that the number so formed is divisible by $5$.

$\therefore U=\{10,15,20,25,30,35,40,45,50\}$
$\therefore n\left(U\right)=9$