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40% of the students at a school take a math class and 60% of the schoo 08 May 2018, 02:51
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D
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35% (medium)

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73% (01:28) correct 27% (01:38) wrong based on 66 sessions

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[GMAT math practice question]

40% of the students at a school take a math class and 60% of the school’s students take a physics class. What percent of students at the school take a math class, but not a physics class?

1) 25% of students take both a math class and a physics class.
2) 25% of students take a physics class, but do not take a math class.

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D
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40% of the students at a school take a math class and 60% of the schoo 08 May 2018, 03:36
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MathRevolution
[GMAT math practice question]

40% of the students at a school take a math class and 60% of the school’s students take a physics class. What percent of students at the school take a math class, but not a physics class?

1) 25% of students take both a math class and a physics class.
2) 25% of students take a physics class, but do not take a math class.
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Lets assume ,
m= % of the students who take only math class
p= % of the students who take only physics class
x= % of the students who take both math & physics class

Thus according to the Q-stem :
\(m+x=40\) .............................eqn A
& \(p+x=60\) .............................eqn B
and we need to find m.

1. \(x= 25\), hence from eqnA we can get m .....................................(Sufficient)
2. \(p= 25\). hence from eqnB we can get x. And then putting the value of x in eqnA we get the value of m..........(Sufficient)

Thus I would go for option D
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40% of the students at a school take a math class and 60% of the schoo 08 May 2018, 03:46
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MathRevolution
[GMAT math practice question]

40% of the students at a school take a math class and 60% of the school’s students take a physics class. What percent of students at the school take a math class, but not a physics class?

1) 25% of students take both a math class and a physics class.
2) 25% of students take a physics class but do not take a math class.
Show more

Let there be 100 students in the school.
If 40% of the students take a math class, P(Only Math) + P(Both) = 40
If 60% of the students take a physics class, P(Only Phy) + P(Both) = 60

1. P(Both) = 25
P(Only Math) = 40 - 25 = 15 (Sufficient)

2. P(Only Phy) = 25
P(Both) = 60 - 25 = 35
Now, P(Only Math) = 40 - 35 = 5 (Sufficient - Option D)

Is it possible for a DS question to have different answers for different statements?
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40% of the students at a school take a math class and 60% of the schoo 08 May 2018, 05:16
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MathRevolution
[GMAT math practice question]

40% of the students at a school take a math class and 60% of the school’s students take a physics class. What percent of students at the school take a math class, but not a physics class?

1) 25% of students take both a math class and a physics class.
2) 25% of students take a physics class, but do not take a math class.
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Dear MathRevolution

This question is flawed because two statements can't contradict each other. Every statement gives different end result.

Bunuel

Can you please advice?
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40% of the students at a school take a math class and 60% of the schoo 08 May 2018, 07:15
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"statement 1 and statement 2 won't contradict each other.
the point is that it will ALWAYS be POSSIBLE to combine the statements -- even if you don't have to."

By Ron Purewal Statements NEVER contradict each other in DS
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40% of the students at a school take a math class and 60% of the schoo 10 May 2018, 07:50
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=>

Forget conventional ways of solving math questions. For DS problems, the VA (Variable Approach) method is the quickest and easiest way to find the answer without actually solving the problem. Remember that equal numbers of variables and independent equations ensure a solution.

This is a typical 2 x 2 matrix question with percentages. To solve it, we need 3 percentages. The original condition provides 2 percentages, so we need only 1 more percentage. Each of the conditions provides 1 percentage, so the VA method tells us that, each condition is likely to be sufficient.

Therefore, D is the answer.
Answer: D

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