Mathematics > Standard Multiple Choice
Read the following SAT test question and then click on a button to select your answer.
Of 5 employees, 3 are to be assigned an office and are to be assigned a cubicle. If 3 of the employees are men and 2 are women, and if those assigned an office are to be chosen at random, what is the probability that the offices will be assigned to 2 of the men and 1 of the women?
(A) 1/3
(B) 2/5
(C) 1/2
(D) 3/5
(E) 2/3
The correct answer is D
Explanation
Of the office workers,
are to be assigned an office. This is an example of combinations: to find the number of ways of choosing
of the
workers, you can count the number of ways of selecting the workers one at a time and then divide by the number of times each group of
workers will be repeated.
There are ways of choosing the first worker to get an office. Then there will be
ways of choosing the second worker to get an office, and
ways of choosing the third worker. This is a total of
possibilities. In these
possible selections, each distinct group of
workers will occur
times. (There are
possibilities for the first worker chosen from the group,
for the second worker chosen, and only
for the third.) Therefore, there are
different ways the
workers who get an office can be chosen from the
workers.
How many of these possible groups of
workers consist of
men and
woman? From the
male workers,
can be chosen in
different ways. There are
possibilities for the female worker. Therefore,
of the groups of
workers consist of
men and
woman.
Since there are different ways the
workers who get an office can be chosen, and
of these possible groups of
workers consist of
men and
woman, the probability that the offices will be assigned to
men and
woman is
, or
.