ronnie1985 wrote:Alicia lives in a town whose streets are on a grid system, with all streets running east-west or north-south without breaks. Her school located on a corner, lies three blocks south and three blocks east of his home, also located on a corner. If Alicia is equally likely to choose any possible path from home to school, and if she only walks south or east, what is the probability that she will walk south for the first two blocks?
I seek the approach
Alicia's trip involves 3 movements south (SSS) and 3 movements east (EEE). We want to know the probability that her first 2 movements are SS. This question is no different from the following:
A bag contains three marbles labeled S and three marbles labeled E. If two marbles are randomly selected from the bag, what is the probability that both are labeled S?
P(SS) = 3/6 * 2/5 = 1/5.
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