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Data Sufficiency

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by vinay1983 » Thu Aug 15, 2013 3:47 am
What is the correct choice?

Q. In a certain class of students, how many boys are there?

1. The class has fewer than 10 students.
2. 10% of the students are boys?

Now my question is I have been told that, if a DS question asks How many, or what is the value....etc, it means we must find a definite value.

So, what is the answer for the above question? A, B, C, D, E. Explain?
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by macattack » Thu Aug 15, 2013 4:11 am
Statement 1: The class has fewer than 10 students.
Here we can have 0 boys, 1 boy, 2 boys...9 boys
Insufficient.

Statement 2: 10% of the students are boys?
But how many students do we have. If we have 10 then 1 student is a boy, if we have 20 then 2 are boys...
Insufficient

The two statements combined: We know that the number of boys should be an integer. Knowing that the class has a number of students<=10 and that 10% are boys--->the only credible answer for the number of boys is 1. (The class has 10 students), since any other number of students below 10 would lead to a non integer number of boys which is not acceptable.

The correct answer is C
The GMAT can be destroyed.
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by Brent@GMATPrepNow » Thu Aug 15, 2013 6:21 am
vinay1983 wrote:What is the correct choice?

Q. In a certain class of students, how many boys are there?

1. The class has fewer than 10 students.
2. 10% of the students are boys?
Are you sure you wrote the question correctly?

Statement 1: If there are fewer than 10 students, then the number of students = 0,1,2,3,4,5,6,7,8 or 9
NOT SUFFICIENT

Statement 2:
NOT SUFFICIENT

Statements 1 & 2 combined:
If 10% of the students are boys, and there are fewer than 10 students, it's impossible to get an integer value for the number of boys. So, this question doesn't make any sense.

The question looks very similar to a question I created for our free DS video called "Avoiding Common Mistakes - Part II" (https://www.gmatprepnow.com/module/gmat- ... cy?id=1105). The video features the following question (at 1:15):

In a certain class of students, how many boys are there?
1. The class has fewer than 20 students.
2. 10% of the students are boys

The answer to this question is C, because we can conclude that the number of students must be 10 (as macattack explained) since this is the only value that provides an integer value for the number of boys.

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
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