Of the 60 students in a certain class, the number of male students who

Question

Of the 60 students in a certain class, the number of male students who use their latop computer in class is how much greater than the number of female students who use their laptop computer in class?

(1) 1/4 of the male students and 1/3 of the female students use their laptop computer in the class.

(2) The ratio of number of male students who use their laptop computers in the class to the number of female students who use their laptop computers in the class is 9 to 8.

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GMATGuruNY · Answer

I've revised the question stem a bit.
Since the number of male students who use a laptop does not have to be greater than the number of female students who use a laptop, the phrase in blue seems appropriate:

Let x = the number of male students who use a laptop and y = the number of female students who use a laptop.
Question stem:
What is the value of |x-y|?

Statement 1: 
Since the x male students who use a laptop constitute 1/4 of all the male students, the total number of male students = 4x
Since the y female students who use a laptop constitute 1/3 of all the female students, the total number of female students = 3x
Resulting equation for all 60 students in the class:
4x+3y = 60

When an equation with two variables is constrained to nonnegative integers, it is possible that the equation will have only one solution.
Before concluding that Statement 1 is insufficient, we should confirm that more than one integer solution is possible for 4x+3y = 60.
To determine all possible solutions for this equation, we can use the method I discuss  here , yielding the following options for x and y:
x=12, y=4
x=9, y=8
x=6, y=12
x=3, y=16
Since |x-y| can be different values, INSUFFICIENT.

Statement 2:
x/y = 9/8
Since x+y cannot exceed 60, the following options are yielded for x and y:
x=9, y=8
x=18, y=16
x=27, y=24
Since |x-y| can be different values, INSUFFICIENT.

Statement combined:
The only combination common to both statements is x=9 and y=8.
Thus, |x-y| = |9-8| = 1
SUFFICIENT.

C

Rahul257 · Answer

Total male students, M =ML(laptop)+MNL(no laptop)
total female students, F=FL(laptop)+FNL(no laptop)
Total students= M+F=60 (given)
We have to find ML-FL

statement 1

ML=1/4M
FL=1/3F
not sufficient

statement 2

ML/FL=9/8
not sufficient

Combining statement 1 and statement 2

60=F+M=3FL+4ML
ML/FL=9/8
60=3FL+4*(9/8)FL
FL=8
ML=9/8*8=9

ML-FL=1

Hence C is the correct answer

GMATGuruNY · Answer

You are correct that Statement 1 as written is insufficient.
But we must be careful.
If the fractions given in Statement 1 were different, they might be sufficient to solve for M and F.
Consider the following revision of the problem:

Here, only one combination of positive integers satisfies Statement 1 while summing to 60:
M=40 and F=20
As a result, Statement 1 is sufficient, making the correct answer A.

pierjoejoe · Answer

that "how much greater" caught me off guard. i really thought that it was talking about "how many times greater" is the number of males who use laptop with respect to female who use laptop. That's the reason why i thought the answer was B.

Rikhraj1 · Answer

Bunuel  pls help me with this one.

Bunuel · Answer

Of the 60 students in a certain class, the number of male students who use their laptop computer in class is how much greater than the number of female students who use their laptop computer in class?

(1) 1/4 of the male students and 1/3 of the female students use their laptop computer in the class.

Assuming there are x male students and 60 - x female students, the difference between males using laptops and females using laptops would be (x/4) - (60 - x)/3 = 7x/12 - 20. We cannot find x, so we cannot find the difference. For example, the number of males, x, and females, 60 - x, could be 12 and 48; 24 and 36; 36 and 24; or 48 and 12. Not sufficient.

(2) The ratio of number of male students who use their laptop computers in the class to the number of female students who use their laptop computers in the class is 9 to 8.

This implies that the number of males using laptops is a multiple of 9 and the number of females using laptops is a corresponding multiple of 8, so those can be: 9 and 8; 18 and 16; or 27 and 24. So, the difference would be 1, 2, or 3. Not sufficient.
 
(1) + (2) The only case from (1) for which 1/4 of x is a multiple of 9 is when x = 36. Thus, there are 36 males and 24 females, giving the users of laptops as 9 and 8. Sufficient.

Answer: C.

Of the 60 students in a certain class, the number of male students who

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GMAT Data Sufficiency (DS) Questions

Of the 60 students in a certain class, the number of male students who

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