Question

An urn contains 4 black, 5 white and 6 red balls. Two balls are drawn one after the other without replacement, what is the probability that at least one ball is black?

Answer 1

Answer:

4/15

Step-by-step explanation:

Answer 2

Answer:

Probability that atleast one ball is black = $\frac{10}{21}$.

Step-by-step explanation:

In the question,

Number of black balls in the urn = 4

Number of white balls in the urn = 5

Number of red balls in the urn = 6

So,

Probability of picking atleast one Black ball = 1 - Probability of picking no Black ball

So,

Probability of picking no Black ball is given by,

$Probability =\frac{11}{15}\times \frac{10}{14}\\\\Probability =\frac{11}{21}$

(∵ There is no Replacement.)

So,

Probability of picking atleast 1 Black ball is,

$1-\frac{11}{21}=\frac{10}{21}$

Therefore, the probability that atleast one ball is black is $\frac{10}{21}$.