An urn contains 10 black and 5 white balls. Two balls are drawn from the nm one after the other without replacement. What is the probability that both drawn balls are black?

Explanation

In first draw, there are 10 black balls and 15 total balls.So,


Probablity of drawn ball is black `= 10/15 = 2/3`

In second draw, there are 9 black balls and 14 total balls.So,


Probablity of drawn ball is black `= 9/14 `

So, probablity of drawing both black balls `=2/3**9/14 = 3/7`