Probability
Aptitude

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Q.

A bag contains 7 green and 5 black balls. Three balls are drawn one after the other. The probability of all three balls being green, if the balls drawn are not replaced will be:

 A.

343/1728

 B.

21/36

 C.

12/35

 D.

7/44

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Solution:
Option(D) is correct

Here, $n(E)$\(=^7C_1\times ^5C_1\times ^5C_1\)

And, $n(S)$\(=^{12}C_1\times ^{11}C_1\times ^{10}C_1\)

\(P(S)=\dfrac{7\times6\times5}{12\times11\times 10 }\)

\(=\dfrac{7}{44}\)


(1) Comment(s)


P V Gopalakrishnan
 ()

It should be 7c1X6c1x5c1