A bag contains 12 white and 18 black balls. 2balls are drawn in succession. What is the probability that first is white and second is black?  Answers:
A) 21/112
B) 36/145
C) 3/115
D) 2/115
E) 3/116
The probability that first ball is white:   =12C130C1=12C130C1   =1230=1230   =25=25   Since, the ball is not replaced; hence the number of balls left in bag is 29.   Hence, the probability the second ball is black:   =18C129C1=18C129C1   =1829=1829   Required probability,   =(25)×(1829)=(25)×(1829)   =36/145   36/145
<result>B</result>
A bag contains 12 white and 18 black balls. 2balls are drawn in succession. What is the probability that first is white and second is black?