A fair coin is tossed until the same result turns up in succession(two head or two tail).Find the probability the number of tosses neede are even..
my approach ..P={P(x=2)+P(x=4)+P(x=6)+...}=0.33
Me answer 2*{P(x=2)+P(x=4)+P(x=6)+...}=0.66
what is the reason of this 2 multiplication?