question_answer 83)

Suppose we have four boxes A, B, C and D containing coloured marbles as given beow :

Box	Marble Colour
	Red	White	Black
A	1	6	3
B	6	2	2
C	8	1	1
D	0	6	4

                  One of the boxes has been selected at random and a single marble is drawn from it. If the marble is reed, what is the probability that it was drawn from box A ? box B? Box C ?  

Answer:

Let E1, E2, E3 and E4 are the events of selection of boxes A, B, C and D respectively.       Let R = event of getting red ball.       We have P(E1) = P(E2) = P(E2) = P(E4) =       and (R/E1) =       R(R/E1) =       P(the red ball is drawn fro the box A)       = P(E2 /R)                         P(the red ball is drawn from the box B) = P(E2/R)                         and P (the red ball is drawn from the box C)             = P(E3/R)