First time here? Checkout the FAQ!
+4 votes

A coin is tossed thrice. Let X be the event that head occurs in each of the first two tosses. Let Y be the event that a tail occurs on the third toss. Let Z be the event that two tails occur in three tosses.
Based on the above information, which one of the following statements is TRUE?

(A) X and Y are not independent (B) Y and Z are dependent
(C) Y and Z are independent (D) X and Z are independent

asked in Numerical Ability by Veteran (41.4k points)   | 225 views

1 Answer

0 votes
so and should be B

  event X =HH _

 event  Y= _ _T      so X and Y are independent  so option A is out

 event Z = 2T 1 H (any order TTH,THT,HTT)  so if X occurs Z can not occur hence X and Z are dependent events so option D is out

event Z = 2T 1 H ( TTH(event Y is not possible hence Y and Z are dependent) ,THT(event Y is possible) ,HTT (event Y is possible)

 consider  choice C and D the question is asked about 2 (exactly 2) tails occur in 3 tosses now if there is a tail in 3rd toss then we need only one tail in first 2 tosses else we need 2 tails   hence they are dependent on each other
answered by Veteran (43.5k points)  
edited by
Can anyone please elaborate i am finding it difficult to understand.

Top Users May 2017
  1. akash.dinkar12

    3308 Points

  2. pawan kumarln

    1884 Points

  3. Bikram

    1656 Points

  4. sh!va

    1640 Points

  5. Arjun

    1396 Points

  6. Devshree Dubey

    1272 Points

  7. Debashish Deka

    1162 Points

  8. Angkit

    1048 Points

  9. LeenSharma

    1010 Points

  10. Arunav Khare

    754 Points

Monthly Topper: Rs. 500 gift card
Top Users 2017 May 22 - 28
  1. Bikram

    742 Points

  2. pawan kumarln

    510 Points

  3. Arnab Bhadra

    490 Points

  4. bharti

    304 Points

  5. LeenSharma

    248 Points

22,832 questions
29,157 answers
27,673 users