A biased coin with probability p, 0 < p < 1 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:
Answer & explanation
Correct answer: option 1
P(Heads in even toss) = P(IInd toss) + P(IVth toss) + ...= P(TH) + P(TTTH) + ....
= (1 – p) . p + (1 – p)3. p + .........