Last Updated on May 6, 2023
GMAT OFFICIAL GUIDE DS
Solution:
We need to determine the number of college graduates in a sample of 80 adults. Because some of the 80 adults are college graduates, while others are not, let’s define two variables:
c = the number of adults who are college graduates
n = the number of adults who are not college graduates
Since there are 80 adults in the random sample, we can create the following equation:
c + n = 80
Statement One Alone:
In the sample, the number of adults who are not college graduates is 3 times the number who are college graduates.
From statement one we can say:
n = 3c
Since n = 3c, we can plug 3c for n into the equation c + n = 80.
c + 3c = 80
4c = 80
c = 20
Thus, there are 20 college graduates. Statement one is sufficient to answer the question. We can eliminate answer choices B, C, and E.
Statement Two Alone:
In the sample, the number of adults who are not college graduates is 40 more than the number who are college graduates.
From statement two, we can say:
n = 40 + c
Since 40 + c = n, we can substitute 40 + c for n into the equation c + n = 80.
c + 40 + c = 80
2c = 40
c = 20
There are 20 college graduates.
Statement two is also sufficient to answer the question.
Answer: D
