✔ 最佳答案
The answer given by the above person is incomplete. he only gave the probability of passing at least one test, i.e., 3/4. However, he has not answered the probability of passing the road test, becasue passing at least one test can mean passing the theory test not the road test.
Here is the complete solution.
Probability of passing at least one test = 3/4 as calculated (not repeating here).
This is made up of three conditions:
(i) Passing both test=> probability = 2/3 * 1/4 = 1/6
(ii) Passing theory test and failing road test=> probability = 2/3 * 3/4 = 1/2
(iii) Failing theory test and passing road test=> probability = 1/3 * 1/4 = 1/12
(i) + (ii)+ (iii) = 1/6 + 1/2 + 1/12 = 3/4.
Thus, given that she passes at least one test [meaning one of the conditions (i), (ii) and (iii)] , the probability that shes passses the road test are actually (i) and (iii), thus it is equal to 1/6 + 1/12 = 1/4