1.  12 persons are seated at a circular table. find the probability that 3 particular persons always seated together?


9/55
7/55
4/55
3/55


Answer

 Option

Total probability = (12 - 1) ! = 11! Desired probability = (10 - 1)! = 9! So, p = ( 9!*3!)/11! = 3/55

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2.  A speak truth in 60% cases and B in 80% cases. In what percent of cases they likely to contradict each other narrating the same incident?


9/25
7/25
11/25
13/25


Answer

 Option

P(A) = 3/5 and P(B) = 4/5. Now they are contradicting means one is telling truth and other telling the lie. So, probability = (3/5)*(1/5)+ (2/5)/4*5

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3.  Out of 14 applicants for a job, there are 6 women and 8 men. it is desired to 2 persons for the job. The probability that atleast one of selected persons will be a woman is?


77/91
54/91
45/91
40/91


Answer

 Option

Man only = 8c2 = 14 Probability of selecting no woman = 14/91 Probability of selecting atleast one woman = 1 - 14/91 = 77/91

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4.  In an examination, there are three sections namely reasoning, maths and english. Reasoning part contains 4 questions. There are 5 questions in maths section and 6 questions english section. If three questions are selected randomly from the list of questions then what is the probability that all of them are from maths?


7/91
8/91
2/91
4/91


Answer

 Option

Total no of questions = 15 probability = 5c3/15c3 = 2/91

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5.  The probability that a person will be alive after 20 years is 1/4 and that of his wife is 2/5. Find out the probability that both are not alive after 20 years?


7/20
9/20
11/20
13/20


Answer

 Option

prob. That man is not alive = 3/4 and that of his wife = 3/5 Prob. That both will be dead = 3/4 * 3/5 = 9/20

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