Latest TCS Aptitude Question SOLUTION: From a pack, two cards are drawn, the probability that either both are black of both are queen is

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(#M40011991) TCS question Keep an EYE

From a pack, two cards are drawn, the probability that either both are black of both are queen is

Asked In TCS (11 years ago)

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jhankar  (11 years ago)

26c2/52c2+4c2/52c2-2c2/52c2
bcoz 2 queens are of black cards..which were counted twice.

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nishi agarwal  (11 years ago)

total no of cards=52
no of black cards=26
no of queens=4
probability of choosing 2 black cards = 26c2/52c2
probability of choosing 2 queens = 4c2/52c2
probability of choosing 1st or 2nd condition = (26c2+4c2)/(52c2)

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juhi sharma  (11 years ago)

26C2/52C2+4C2/52C2...

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Denis  (11 years ago)

Probability of choosing 2 black cards =(26/52)*(26/52)=1/4
Probability of choosing queen= (4/52)*(4/52)=1/169
But first case also contains the condition of selecting 2 queens as the 2 black cards could be 2 queens,thus
total probability=(1/4)+(1/169)-(1/13), where (1/13) is the conditional probability p(queenblack)=(p(queen intersection black))/p(black)

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