Question

A bag contains 6 white and 4 black balls .2 balls are drawn at random. find the probability that they are of same colour.

Answer 1

let S be the sample space 

Then n(S)=no of ways of drawing 2 balls out of (6+4)=10c2=(10*9)/(2*1)=45 

Let E=event of getting both balls of same colour 

Then n(E)=no of ways(2 balls out of six) or(2 balls out of 4)

=(⁶ c₂+⁴ c₂)=(6*5)/(2*1)+(4*3)/(2*1)=15+6=21

P(E)=n(E)/n(S)=21/45=7/15