Graduate Management Admission Test (GMAT) Practice Test

What is the probability that a randomly selected student at a riding school will be assigned a horse of the same sex?

1. (40 + 18) / 121

2. (5 + 6) / 121

3. (8 + 3) / 121

4. (11 + 9) / 121

The correct answer is: (40 + 18) / 121

To determine the probability that a randomly selected student at the riding school will be assigned a horse of the same sex, we first need to understand how probabilities are generally calculated. The probability of an event occurring is given by the ratio of the number of favorable outcomes to the total number of possible outcomes. In this context, we define favorable outcomes as the instances where the student is matched with a horse of the same sex. It's important to look at the numbers provided in the choices because they represent counts of different pairs (students and horses) that are likely being totaled based on their respective sexes. The correct answer combines two groups: one group of students matched with horses of one sex and another with horses of the opposite sex; thus, the selection of horses of the same sex is represented by the sum of these counts. The formula given in the selected answer includes the total number of scenarios where there is a match divided by the total number of students and horses, resulting in (40 + 18) as favorable outcomes and 121 representing the total. This means that there is a total of 121 scenarios when considering all students and horses, and a selection of horses matches the same sex with students in 58 of those cases (the sum provided in the correct