MathematicsMedium75×since 2002Q5004A 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 X\mathrm{X}X denotes the number of tosses of the coin, then the mean of X\mathrm{X}X is :A8164\frac{81}{64}6481B3716\frac{37}{16}1637C2116\frac{21}{16}1621D1516\frac{15}{16}1615Check answerSkip