GMAT Quantitative Reasoning Practice Test 1

If you are randomly guessing with five possible answer choices, the probability of guessing correct is 1 out of 5, or

1

5

. Since the test has n number of questions and we want to get half of them correct, we want this to happen

n

2

times. Therefore, the probability would be

1

5

times itself

n

2

times, or (

1

5

)

n

2

.