Latest TCS Aptitude Question SOLUTION: A bag contains 6 balls of one or more colors. A ball is picked and is found to be red. What is the probability that the bag initially had exactly 6 red balls? option a) 2/7 b) 1/5

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A bag contains 6 balls of one or more colors. A ball is picked and is found to be red. What is the probability that the bag initially had exactly 6 red balls?
option
a) 2/7
b) 1/5
c) 3/5
d) 4/5

Asked In TCS TCS 2014 (10 years ago)

Unsolved Read Solution (6)

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Read Solution (6) :

Swarnali Biswas  (10 years ago)

Ans :2/7

If we have 1 red ball then the probability of drawing 1 red ball out of 6 balls is 1/6

If there are 2 red balls then the probability of drawing 1 red ball out of them is 2c1/6

similarly the other cases 3/6 4/6 5/6 6/6..

Now the probability of drawing 1 red ball when all the six are red is
[6/6]/[(1/6)+(2/6)+(3/6)+(4/6)+(5/6)+(6/6)]
6/21=2/7..

Is this solution Helpfull? Yes (85) | No (3)  

Pavani  (9 years ago)

its simple.consider all the possible cases
there are 6 cases of having red balls
P(only 1 is red and it is selected out of 6 balls)=1/6
P(2 balls are red and 1 is selected of them)=2/6
similarly remaining probabilities are 3/6,4/6,5/6,6/6
now the required question asks us to compare the event of all 6 being red with all the possible eventsa
Probability=(6/6)/((1/6)+(2/6)+(3/6)+(4/6)+(5/6)+(6/6))
=6/(6*7/2)
=2/7

Is this solution Helpfull? Yes (8) | No (1)  

Guru Pranav  (10 years ago)

6/21

Is this solution Helpfull? Yes (4) | No (3)  

Mudassir Fazal  (10 years ago)

when one red ball has come out then there must be atleast one red ball in bag.
from other remaining 5 balls. 1 can be red
2 can be red
3 can be red
4 can be red
5 can be red
so there are 5 cases out of one is favourable
probablity=1/5

Is this solution Helpfull? Yes (2) | No (19)  

Chirag Ranjan Lahiri  (9 years ago)

If we have 1 red ball then the probability of drawing 1 red ball out of 6 balls is 1/6

If there are 2 red balls then the probability of drawing 1 red ball out of them is 2c1/6

similarly the other cases 3/6 4/6 5/6 6/6..

Now the probability of drawing 1 red ball when all the six are red is
[6/6]/[(1/6)+(2/6)+(3/6)+(4/6)+(5/6)+(6/6)]
6/21=2/7..........

Is this solution Helpfull? Yes (2) | No (1)  

varsha rai  (9 years ago)

ans is 1/5
since there are 6 balls which can be of one or more colours.
one is taken out and is found to be red
left balls in the bag are 5
and one is out so automatically the probability of getting 6 red balls initially is 1/5.

Is this solution Helpfull? Yes (1) | No (3)  

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