ajisha wrote:

out of 100 each ticket has 1/2 probability of winning. So we have 50 winning and 50 non-winning tickets.

Now selecting 2 out of non-winning.

50/100 * 49/99

= 49/198 probabillity of non -winning tickets

Atleast one winning means 1-49/198 = 149/198

D.

Hope this helps.

i have never taken a class in probability theory, but I have been reading up on it and is "each ticket has a 1/2 chance of winning" necessarily the same thing as "there are 50 winning tickets"

i'm not so keen on that. on the surface you can say "sure it is" but think about the binomial distribution of flipping a coin 100 times. you've got outliers where you can have 100 heads and 100 tails.

100 tickets each with 1/2 chance of winning means that it is possible for all 100 tickets to win. likewise it is possible for none of the tickets to be winners.

the question stem should say there are 100 lotto tickets, of which 50 are winning tickets. the difference may seem subtle, but implications on the correct calculation are not.

IMHO, this question is junk. If you approach it from the angle presented, it is completely illogical. If there are a 100 tickets; 50 of which are winners, each ticket DOES NOT have a 1/2 chance of winning. whether a ticket is a winner or loser has already been determined. Therefore the ticket IS A WINNER (P=1) or IS NOT A WINNER (P=0). Chance does not come into play whether it is a winner or a loser, it either is or isn't. If this is the case, then the answer is D. but the way the question is written is a mess.

It is hard to explain, but sit and think about it what i am saying for a while.