In a group of 80 college students, how many own a car?

The value of 'a' can be zero as well, at least mathematically as that would also justify above conditions. Of course, that makes the statement 2 a tad impractical, but still correct mathematically. So, the value of 'a' can not be ascertained for sure and the answer should still be E.

A bit of an ambiguous question for sure. Maybe the questions needs to mention that a and b are non-zero or something.

a can not be zero.

if a is zero, how can 42% of it be females?

think again !!

It can be 0 and then 42% of the same would also be 0 (number of females). Where does it say in the question that number of females have to be non-zero. All we know is that females = 0.42*a and this equation can be valid at both a = 0 and a = 50 without contradicting anything given in the question.

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(2) Of the students who own a car, 42% are female.

The phrase 'Of the students who own a car' already tells you that some students own a car, so it is not a possibility that 0 students own a car. Further, if I were to tell you that 0 people own a car, and I asked you what percentage of the students who own a car are female, you would not say "42%". It would be meaningless to assign a percentage in that case. The GMAT would never tell you '42% of people own a car' and then make the 'trap' that 0 people might own a car, because most test takers would, very reasonably, assume the number of car owners needs to be non-zero.

So if you see a phrase like '1/3 of the people in North America who own a computer are Canadian' or '45% of the marbles in a bag are green', you can certainly assume that the number of North Americans who own a computer, or the number of marbles in the bag, is not zero.

Ian very nice explanation.

beyondgmatscore: I advice you not to assume too much on GMAT. DS would be hard to crack if you make such assumptions.

Thanks Ian and Gurpreet.

In a group of 80 college students, how many own a car?

(1) Of the students who do not own a car, 14 are male. Clearly insufficient.

(2) Of the students who own a car, 42% are female --> let # of students who own a car be \(x\) --> \(0.42x=\) # of females who own a car. But \(0.42x\) must be an integer, as it represent # of females. \(0.42x=integer\) --> \(\frac{21}{50}x=integer\) --> \(x\) is a multiple of 50: 50, 100, 150, ... But \(x\) (# of students who own car) must also be less than (or equal to) 80. So \(x=50\). sufficient.

Answer: B.

OPEN DISCUSSION OF THIS QUESTION IS HERE: in-a-group-of-80-college-students-how-many-own-a-car-95019.html