Last Updated on May 10, 2023
GMAT OFFICIAL GUIDE DS
Solution:
We need to determine the amount that Jean earned from the commission on her sales in the first half of 1988.
Statement One Alone:
In 1988 Jean’s commission was 5 percent of the total amount of her sales.
Before analyzing statement one let’s define some variables:
a = Jean’s commission in the first half of 1988
b = Jean’s commission in the second half of 1988
A = Jean’s total sales in the first half of 1988
B = Jean’s total sales in the second half of 1988
We are trying to determine the value of a. In statement one we are given that in 1988 Jean’s commission was 5 percent of the total amount of her sales. Translating this into an equation gives us:
(a + b)/(A + B) = 0.05
Since we cannot determine a value for a, statement one alone is not sufficient to answer the question. We can eliminate answer choices A and D.
Statement Two Alone:
The amount of Jean’s sales in the second half of 1988 averaged $10,000 more per month than in the first half.
Using the information in statement two we can create the following equation:
B/6 = (A/6) + 10,000
Multiplying the entire equation by 6 we obtain:
B = A + 60,000
Since we cannot determine a value for a, statement two alone is not sufficient to answer the question. We can eliminate answer choice B.
Statements One and Two Together:
From statements one and two we have the following two equations:
1) (a + b)/(A + B) = 0.05
2) B = A + 60,000
We see that even if we substitute A + 60,000 for B in the equation (a + b)/(A + B) = 0.05, we still do not have enough information to determine the value of a.
Answer: E
