Question

Lizabeth lives in San Francisco and works in Mountain View. In the morning, she has 333 transportation options (take a bus, a cab, or a train) to work, and in the evening she has the same 333 choices for her trip home.

If Elizabeth randomly chooses her ride in the morning and in the evening, what is the probability that she'll use a cab exactly one time?

Answer 1

4/9

Explanation:

B = bus

C = cab

T = train

Going Returning

B B

B C <---- one cab

B T

C B <---- one cab

C C

C T <---- one cab

T B

T C <---- one cab

T T

There is a total of 9 possible different outcomes of her 2 choices as listed above.

Above we see above, there are 4 outcomes with exactly one cab ride.

p(exactly one cab ride) = 4/9