Probability Questions Answers

Probability Questions Answers (MCQ) listings with explanations includes questions of determining chances of happening an event in different type of problems using different methods which are important for many competitive exams.

11) Three unbiased coins are tossed, what is the probability of getting at least 2 tails

  • 1) 1/3
  • 2) 1/6
  • 3) 1/2
  • 4) 1/8
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Ans.   C
Explanation :
Total cases are = 2*2*2 = 8, which are as follows [TTT, HHH, TTH, THT, HTT, THH, HTH, HHT] Favoured cases are = [TTH, THT, HTT, TTT] = 4 So required probability = 4/8 = 1/2

12) In a throw of dice what is the probability of getting number greater than

  • 1) 1/2
  • 2) 1/3
  • 3) 1/5
  • 4) 1/6
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Ans.   D
Explanation :
Number greater than 5 is 6, so only 1 number Total cases of dice = [1,2,3,4,5,6] So probability = 1/6

13) What is the probability of getting a sum 9 from two throws of dic

  • 1) 1/3
  • 2) 1/9
  • 3) 1/12
  • 4) 2/9
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Ans.   B
Explanation :
Total number of cases = 6*6 = 36 Favoured cases = [(3,6), (4,5), (6,3), (5,4)] = 4 So probability = 4/36 = 1/9

14) Two dice are thrown simultaneously. What is the probability of getting two numbers whose product is even

  • 1) 3/4
  • 2) 1/4
  • 3) 7/4
  • 4) 1/2
View Answer View Explanation
Ans.   A
Explanation :
Total number of cases = 6*6 = 36 Favourable cases = [(1,2),(1,4),(1,6),(2,1),(2,2),(2,3),(2,4),(2,5),(2,6),(3,2),(3,4),(3,6),(4,1),(4,2),(4,3),(4,4),(4,5),(4,6),(5,2),(5,4),(5,6),(6,1),(6,2),(6,3),(6,4),(6,5),(6,6)] = 27 So Probability = 27/36 = 3/4

15) Two unbiased coins are tossed. What is probability of getting at most one tail

  • 1) \begin{aligned} \frac{1}{2} \end{aligned}
  • 2) \begin{aligned} \frac{1}{3} \end{aligned}
  • 3) \begin{aligned} \frac{3}{2} \end{aligned}
  • 4) \begin{aligned} \frac{3}{4} \end{aligned}
View Answer View Explanation
Ans.   D
Explanation :
Total 4 cases = [HH, TT, TH, HT] Favourable cases = [HH, TH, HT] Please note we need atmost one tail, not atleast one tail. So probability = 3/4
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