Question

A fair coin is flipped three times. Events A and B are defined as: A: there are at least two consecutive heads somewhere in the sequence B: at least one flip comes up tails What is p(A | B)?

Answer 1

Answer:

2 / 7

Step-by-step explanation:

Coin flipped 3 times has following outcomes, of heads 'H' & Tails 'T'

HHH , TTT , HTT, THT , TTH , THH , HTH , HHT  = total outcomes

P (A) = 2 consecutive heads , P (B) = atleast one tail

P (A) = 2 outcomes ( HHH , HHT , THH ) / total 8 outcomes = 3 / 8

P (B) = 7 outcomes (all except HHH) / total 8 outcomes = 7 / 8

P (A | B) = P ( A ∩ B ) / P (B)

P ( A ∩ B ) = P ( 2 consecutive heads & atleast one tail) / Total outcomes =   2 outcomes ( HHT , THH ) / total 8 outcomes = 2 / 8

So, P (A | B) = ( 2 / 8 ) /  ( 7 / 8 ) = 2 / 7