A odd number lie between 0 and 11(0 and 11 not included), it means that total of ten numbers, starting from {1,2,3........,10} form our sample space.
sample space=s={1,2,3....,10}=total 10 numbers
So,
m=total no. of odd numbers{1,3,5,7,9} in our sample space=5 numbers
probability that number is odd=p=m/s
p=5/10=0.5
