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14.Probability
hard
A box contains $10$ mangoes out of which $4$ are rotten. $2$ mangoes are taken out together. If one of them is found to be good, the probability that the other is also good is
A
$\frac{1}{3}$
B
$\frac{8}{{15}}$
C
$\frac{5}{{18}}$
D
$\frac{2}{3}$
Solution
(c) Number of ways of selecting two good mangoes $= $$^6{C_2} = 15$.
Number of ways that at least one of the two selected mangoes is to be good $ = {}^6{C_1} \times {}^9{C_1} = 54$
$\therefore $ Required probability $ = \frac{{15}}{{64}} = \frac{5}{{18}}$.
Standard 11
Mathematics