A fair die is rolled (2n+1) times.The probability that the faces with even number show odd number of times is-

a) (3n+1)/(4n+2) b) 3/4
c)2/3 d)1/2

Question

A fair die is rolled (2n+1) times.The probability that the faces with even number show odd number of times is-

a) (3n+1)/(4n+2)             b) 3/4
c)2/3                                 d)1/2

anonymous · Answer

The whole roll 2n+1 times, get k even numbered die is a binomial distribution but I wonder

anonymous · Answer

if the symmetry of the probability can't make this a bit easier.

anonymous · Answer

We can definitely use the fact that it is multiple choice though...

anonymous · Answer

If $n=0$ then clearly getting an even face means you win, so the probability is $1/2$.

anonymous · Answer

Which knocks out b and c

anonymous · Answer

i am getting d as the answer , but the book is saying a.

anonymous · Answer

When $n=1$. what is the probability?

anonymous · Answer

You have three rolls, if you roll 1 or 3 evens, you win

anonymous · Answer

hm,yes

anonymous · Answer

oops, that doesn't actually matter, when $n=1$ then a) is still 1/2

anonymous · Answer

They need to be different.

anonymous · Answer

n=2 gives 7/10 for a, but d is still 1/2 so....
5 rolls, what is the probability of odd even rolls

anonymous · Answer

Weird...
There is no explanation for a)?

anonymous · Answer

D i think