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 General Aptitude
 Probability
1.
Three different dice are rolled three times. The probability that they show different numbers only two times is.

A.
100 243_{} 
C.
5_{} 9_{}

B.
1_{} 3_{} 
D.
107_{} 54_{}
 Answer & Explanation
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Answer : [C]
Explanation :
Explanation :
Total no. of cases = 6^{3} = 216  
The number of cases, when all the three numbers are distinct = 6P_{3}  




2.
An urn contains 9 red, 7 White and 4 black balls. If two balls are drawn at random, find the probability that one is white and other red.

A.
67 190_{} 
C.
71_{} 190_{}

B.
73_{} 190_{} 
D.
63_{} 190_{}
 Answer & Explanation
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Answer : [D]
Explanation :
Explanation :
There are totally 20 balls in the bag out of which 2 balls can be drawn in 20C_{2} ways = 190 ways.  
Out of 7 white balls one white ball can be drawn in 7C_{1} ways and out of 9 red balls one red ball cab be drawn in 9C_{1} ways.  
One white and one red ball can be drawn in = 9C_{1} x 7C_{1} ways = 63 ways  


3.
In a single throw of a die, What is the probability of getting a number greater than 4?

A.
1 2 
C.
2 3

B.
1 3 
D.
1 4
 Answer & Explanation
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Answer : [B]
Explanation :
Explanation :
When a die is thrown, we have S = {1, 2, 3, 4, 5, 6}  
Let E = event of getting a number greater than 4 = {5, 6}  


4.
There are two boxes A and B. A contains 3 white balls and 5 black balls and box B contains 4 white and 6 black balls. One box is taken at random and one ball is picked up at random. What is the probability that the ball picked up may be a white one?

A.
3 20_{} 
C.
3_{} 16_{}

B.
3_{} 40_{} 
D.
31_{} 80_{}
 Answer & Explanation
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Answer : [D]
Explanation :
Explanation :
The required probability is the sum of (box A is selected and a white ball is picked up) + (box b is selected and a white ball is picked up)  


5.
A person throws a die, as many times till he gets 6. What is the probability that he will get 6 in the fourth throw?

A.
5^{3} 6^{4} 
C.
5_{} 36_{}

B.
5^{4} 6^{5} 
D.
5_{} 6_{}
 Answer & Explanation
 Report
Answer : [A]
Explanation :
Explanation :





