Question

A bag contains S white and 4 green balls. Two balls are drawn from the bag at random. Find the probability that they are: 

1. of the same colour. 

2. of different colours.

Answer 1

n = Two balls can be drawn from 5 white and 4 green balls in 9C₂ 

= 36 ways.

1. m = 2 balls of the same colour can be drawn in (2 W or 2 G) 

= (5C₂ × 4C₂) 

= (10 + 6) = 16 ways. 

Let P(A) = P( 2 balls of the same colour) 

= m/n = 16/36 =4/9

2. P(A¹ ) = P(2 balls of different colours) 

= 1 P(A) = 1- 4/9 = 5/9.