Question

A box contains 4 black ball 3 red ball and 5 green ball.2 ball ate drawn from the box at random.What is the probability that both the balls are of same colour

Answer 1

Total balls = 4 + 3 + 5 = 12 

Out of 12, we are drawing 2 balls at random 

The 2 balls can be drawn in 12C2 ways. 

Then probability both balls are of same colour 

= 4C2 + 3C2 + 5C2/ 12C2

= 3+6+10/6×11=19/66