A box contains 15 black and 20 white balls. W | vedclass

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(A) Total number of balls $= 15 + 20 = 35$.Total number of ways to select $2$ balls from $35$ is given by ${}^{35}C_{2} = \frac{35 	imes 34}{2 	imes

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$\frac{38}{119}$

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(A) Total number of balls $= 15 + 20 = 35$.Total number of ways to select $2$ balls from $35$ is given by ${}^{35}C_{2} = \frac{35 	imes 34}{2 	imes 1} = 35 	imes 17 = 595$.Number of ways to select $2$ white balls from $20$ white balls is given by ${}^{20}C_{2} = \frac{20 	imes 19}{2 	imes 1} = 10 	imes 19 = 190$.The probability of selecting both white balls is $P = \frac{{}^{20}C_{2}}{{}^{35}C_{2}} = \frac{190}{595}$.Dividing both numerator and denominator by $5$,we get $P = \frac{38}{119}$.

$A$ box contains $15$ black and $20$ white balls. What is the probability that when $2$ balls are selected,both are white?

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