skamal7 wrote:
my question is why in first question probability is calculated and for the second questions they are doing the same thing twice why? i am expecting an answer to be from probability point of view oly
As I have mentioned in my post above, the reason the probabilities are added is to take into account the order in which the interview was taken i.e. if the order to the interview was {Jose, Joshua} or {Joshua,Jose}. Lemme walk you thru the answer.
The probability of randomly choosing {Jose} from the set of 6 workers is clearly 1/6. Now after already have chosen one, the probability to choose the {Joshua} or any other worker would be 1/5
So the net probability of the interview order{Jose, Joshua} is 1/5*1/6 = 1/30. (Let it be P1)
Now, since the assumption to be made here is the interview order matters i.e. the interviews are one-on-one. The other possible order would be {Joshua, Jose}
The probability to happening of the above order is also 1/30 (Let it be P2). Hence the final Probability of both the possible cases is P1 + P2 = 1/30 + 1/ 30 = 1/15.
But, in the first question, 2 people are supposed to go to a conference from a group of 5. The order here i.e. {Marnie, Noomi} or {Noomi,Marnie} does not matter. Hence the probability of choosing any random person from either (Marie or Noomi) in a group of 5 = 2/5
And then, the probability of choosing the next person from (Marie or Noomi) in a group of 4 = 1/4
Final probability = 2/5 * 1/4 = 1/10
Hope this satisfies your query! Would appreciate it if the mods had a look at it and correct me if I am wrong
Regards,
Arpan