A box contains N cons, m of which are fair and the rest are biased. The probability of getting a head when a fair coin is tossed is \[\frac{1}{2},\] while it is \[\frac{2}{3}\] when a biased coin is tossed. A coin is drawn from the box at random and it tossed twice. Then the probability that the coin drawn is fair, is

A box contains N cons, m of which are fair and the rest are biased. Th

1.	A box contains N cons, m of which are fair and the rest are biased. The probability of getting a head when a fair coin is tossed is \[\frac{1}{2},\] while it is \[\frac{2}{3}\] when a biased coin is tossed. A coin is drawn from the box at random and it tossed twice. Then the probability that the coin drawn is fair, is
A.	\[\frac{9m}{8N+m}\]
B.	\[\frac{9m}{8N-m}\]
C.	\[\frac{9m}{8m-N}\]
D.	\[\frac{9m}{8m+N}\]
Answer» B. \[\frac{9m}{8N-m}\]

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