41. The chance of a student passing an exam is 20%. The chance of a student passing the exam and getting above 90% marks in it is 5%, Given that a student passes the examination, the probability that the student gets above 90% marks is
    

1. 1. 1

      18

      
      

   
   
   

   2. 1

      4

      
      

   
   
   

   3. 2

      9

      
      

   
   
   

   4. 5

      18

   
   
   

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1. View Hint View Answer Discuss in Forum

   Given that the student is passing exam, i.e., if only 20 students (out of 100) are considered, of the 5 students get more than 90%
   ∴ 5 out of 20 is the probability or 1/4 is the answer.
   Alternative Method :
   Let the student pass the examination be A and student pass the examination and got about 90% marks be B Now P(A) = 20% and P(A ∩ B) = 5%
   

   ∴ P		B		=	P(A ∩ B)	=	5%	=	1
   		A			P(A)		20%		4

   Correct Option: B

   Given that the student is passing exam, i.e., if only 20 students (out of 100) are considered, of the 5 students get more than 90%
   ∴ 5 out of 20 is the probability or 1/4 is the answer.
   Alternative Method :
   Let the student pass the examination be A and student pass the examination and got about 90% marks be B Now P(A) = 20% and P(A ∩ B) = 5%
   

   ∴ P		B		=	P(A ∩ B)	=	5%	=	1
   		A			P(A)		20%		4

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42. If P(X) =	1	, P(Y) =	1	and P(X ∩ Y) =	1	,the value of P(Y/X) is
    	4		3		12

1. 1. 1

      4

      
      

   
   
   

   2. 4

      25

      
      

   
   
   

   3. 1

      3

      
      

   
   
   

   4. 29

      50

      
      

   
   
   

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1. View Hint View Answer Discuss in Forum

   P(Y / X) =	P(X ∩ Y)	=	1		=	1
   			12
   	P(x)		1			3
   			4

   Correct Option: C

   P(Y / X) =	P(X ∩ Y)	=	1		=	1
   			12
   	P(x)		1			3
   			4

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43. Consider an unbiased cubic dice with opposite faces coloured identically and each face coloured red, blue or green such that each colour appears only two times on the dice. If the dice is thrown thrice, the probability of obtaining red colour on top face of the dice at least twice is _____.

1. 1. 27 /2

   
   
   

   2. 7 /21

   
   
   

   3. 27 /21

   
   
   

   4. 7 /27

   
   
   

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1. View Hint View Answer Discuss in Forum

   p =	2	=	1
   	6		3

   
   

   q = 1 -	1	=	2
   	3		3

   
   using Binomial distribution
   

   p(x ≥ 2) = 3C2		1		2		2		1	+ 3C3		1		3		2		0
   		3				3					3				3

   
   

   =	6	+	1	=	7
   	27		27		27

   Correct Option: D

   p =	2	=	1
   	6		3

   
   

   q = 1 -	1	=	2
   	3		3

   
   using Binomial distribution
   

   p(x ≥ 2) = 3C2		1		2		2		1	+ 3C3		1		3		2		0
   		3				3					3				3

   
   

   =	6	+	1	=	7
   	27		27		27

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44. A group consists of equal number of men and women. Of this group 20% of the men and 50% of the women are unemployed. If a person is selected at random from this group, the probability of the selected person being employed is _______ .

1. 1. 95%

   
   
   

   2. 65%

   
   
   

   3. 75%

   
   
   

   4. 61%

   
   
   

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1. View Hint View Answer Discuss in Forum

   Total% of employed person = 100 -		20 + 50		= 65%
   		2

   Correct Option: B

   Total% of employed person = 100 -		20 + 50		= 65%
   		2

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45. A box contains 25 parts of which 10 are defective. Two parts are being drawn simultaneously in a random manner from the box. The probability of both the parts being good is
    

1. 1. 7

      20

      
      

   
   
   

   2. 45

      125

      
      

   
   
   

   3. 25

      29

      
      

   
   
   

   4. 5

      9

   
   
   

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1. View Hint View Answer Discuss in Forum

   Required Probability =	15C2	=	15 × 14	=	7
   	25C2		25 × 24		20

   Correct Option: A

   Required Probability =	15C2	=	15 × 14	=	7
   	25C2		25 × 24		20

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