A fair coin is tossed until one of the two sides occurs twice in a row. The probability that the number of tosses required is even is

A biased coin with probability P,(0 lt p ,1) of heads is tossed until a head appear for the first time. If the probability that the number of tosses required is even is 2/5 then p=

A baised coin with probability p, 0lt p lt of heads is tossed until a head appears for the first time. If the probability that the number of tosses required is even is 2/5, then p is equal to

A biased coin with probability p,0

A biased coin with probability p, 0ltplt1 of heads is tossed until a head appears for the first time. If the probability that the number of tosses required is even is 2/5, then p equals

A coin is tossed until one observes a sequences three tails , the probability that the experiment comes to an end at the seventh toss is :