Elizabeth lives in San Francisco and works in Mountain View. In the morning, she has 3 transportation options (take a bus, a cab, or a train) to work, and in the evening she has the same 3 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?

4/9

Step-by-step explanation:

The possibilities of transportation: (The first will be for morning, second will be for afternoon)

B, B

B, C

B, T

C, B

C, C

C, T

T, B

T, C

T, T

It is clearly seen that there are 9 transportation options.

(Using cab 1 time we have BC, CB, CT, TC. So four of the transportation methods use cab one time.)

Therefore, the probability that she will use a cab only once is 4/9.  

where are the options?

step-by-step explanation:

x + 4/7

step-by-step explanation:

use cymath