Latest Infosys Aptitude Question SOLUTION: A bag contains 4 white, 5 red and 6 blue balls. Three balls are drawn at random from the bag. The probability that all of them are red, is: a)1/22 b)3/22 c)2/91 d)2/77

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A bag contains 4 white, 5 red and 6 blue balls. Three balls are drawn at random from the bag. The probability that all of them are red, is:
a)1/22
b)3/22
c)2/91
d)2/77

Asked In Infosys (12 years ago)

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abhishek kumar singh  (9 years ago)

the total sample space=15c3=455
now for the red color arrangement possible for all red=5c3=10
again p=n(E)/n(s)=10/455=2/91 thus option C

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Dr.Dipin Singh  (12 years ago)

c)2/91


The probability that all of them are red, is = (5/15)*(4/14)*(3/13)= 2/91 ... option C

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ragu  (5 years ago)

A bag contains 4 white, 5 red and 6 blue balls. Three balls are drawn at random from the bag. The probability that all of them are red, is:

A.
1
22
B.
3
22
C.
2
91
D.
2
77
Answer: Option C

Explanation:

Let S be the sample space.

Then, n(S) = number of ways of drawing 3 balls out of 15
= 15C3
= (15 x 14 x 13)
(3 x 2 x 1)
= 455.
Let E = event of getting all the 3 red balls.

n(E) = 5C3 = 5C2 = (5 x 4) = 10.
(2 x 1)
P(E) = n(E) = 10 = 2 .
n(S) 455 91

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