JEE Math Practice Question
A coin is biased so that the head is 3 times as likely to occur as tail. This coin is tossed until a head or three tails occur. If $$\mathrm{X}$$ denotes the number of tosses of the coin, then the mean of $$\mathrm{X}$$ is :
- A.$$\frac{81}{64}$$
- B.$$\frac{37}{16}$$
- C.$$\frac{21}{16}$$
- D.$$\frac{15}{16}$$
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