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14.Probability
medium
In a box there are $2$ red, $3$ black and $4$ white balls. Out of these three balls are drawn together. The probability of these being of same colour is
A
$\frac{1}{{84}}$
B
$\frac{1}{{21}}$
C
$\frac{5}{{84}}$
D
None of these
Solution
(c) Total number of ways in which $3$ balls can be drawn are ${}^9{C_3} = 84.$
Since the drawn balls can’t be of red colour, as these are $2$ in numbers.
Therefore favourable number of ways $ = {}^3{C_3} + {}^4{C_3}.$
Hence the required probability $ = \frac{5}{{84}}.$
Standard 11
Mathematics
