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Bunuel
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Hi,

Hope zero can be considered rite?

If its taken, then the answer is E. Kindly debrief?

Zero is an even integer, so the answer is still C.
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I think this is a high-quality question and I agree with explanation.
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amazing questions
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(1)+(2) Sum (1) and (2) (x+y)+(x−y)=odd1+odd2(x+y)+(x−y)=odd1+odd2, so 2x=even2x=even. This implies that x=integerx=integer and therefore y=integery=integer. Hence sufficient.

Can someone explain how 2x= even implies , X is an integer
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(1)+(2) Sum (1) and (2) (x+y)+(x−y)=odd1+odd2(x+y)+(x−y)=odd1+odd2, so 2x=even2x=even. This implies that x=integerx=integer and therefore y=integery=integer. Hence sufficient.

Can someone explain how 2x= even implies , X is an integer

2x = even;

x = even/2 = integer.
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Hey Bunuel,

Can you explain how "2x= even" implies , X is an integer

When x = 1.6, 2*1.6 = 3.2 which is an even number.
When x = 2, 2*2 = 4 which is an even number.

Therefore x may or may not be an integer. Hence, the answer should be E - BOTH STATEMENTS ARE INSUFFICIENT
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rogueassasin
Hey Bunuel,

Can you explain how "2x= even" implies , X is an integer

When x = 1.6, 2*1.6 = 3.2 which is an even number.
When x = 2, 2*2 = 4 which is an even number.

Therefore x may or may not be an integer. Hence, the answer should be E - BOTH STATEMENTS ARE INSUFFICIENT

3.2 is NOT an even number.

An even number is an integer that is "evenly divisible" by 2, i.e., divisible by 2 without a remainder. So, ..., -4, -2, 0, 2, 4, ... are all even integers.

An odd number is an integer that is not evenly divisible by 2. So, ..., -3, -1, 1, 3, 5, ... are all odd integers.

For more check here:
ALL YOU NEED FOR QUANT ! ! !
Ultimate GMAT Quantitative Megathread

Hope it helps.
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I have edited the question and the solution by adding more details to enhance its clarity. I hope it is now easier to understand.
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Bunuel
Official Solution:


Is \(10xy\) an even integer?

In order for \(10xy=2*5xy\) to be even, \(5xy\) must be an integer. In this case, \(10xy=2*5xy\) would be \(2*integer\), which is an even number. Hence, essentially, the question is asking whether \(5xy\) is an integer.

However, it's important to note that \(x\) and \(y\) themselves don't necessarily have to be integers for \(5xy\) to be an integer. For instance, if \(x=\frac{7}{9}\) and \(y=\frac{9}{7}\), \(5xy\) is an integer. Nonetheless, if both \(x\) and \(y\) are integers, then \(5xy\) is certainly an integer, thereby making \(10xy\) even.

(1) \(7 + x + y\) is an even integer.

Since \(7+x+y\) is even, then \(x+y\) must be odd. If \(x=1\) and \(y=2\), the answer will be YES. However, if \(x=1.3\) and \(y=1.7\), the answer will be NO. Not sufficient.

(2) \(x-y\) is an odd integer.

If \(x=1\) and \(y=2\), the answer will be YES. However, if \(x=1.3\) and \(y=0.3\), the answer will be NO. Not sufficient.

(1)+(2) From (1) we know that \(x+y=odd\) and from (2) we know that \(x-y=odd\). Adding these two equations gives \((x+y)+(x-y)=odd_1+odd_2\), which results in \(2x=even\). This implies that \(x=\frac{even}{2}\), which is an integer, and thus \(y\) is also an integer. Therefore, \(10xy=10*integer=even\). Sufficient.


Answer: C
---------------

Hi Bunuel, how do we know this is 10*x*y? While first attempting the question I thought x and y are the tens and ones place respectively.
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Bunuel
Official Solution:


Is \(10xy\) an even integer?

In order for \(10xy=2*5xy\) to be even, \(5xy\) must be an integer. In this case, \(10xy=2*5xy\) would be \(2*integer\), which is an even number. Hence, essentially, the question is asking whether \(5xy\) is an integer.

However, it's important to note that \(x\) and \(y\) themselves don't necessarily have to be integers for \(5xy\) to be an integer. For instance, if \(x=\frac{7}{9}\) and \(y=\frac{9}{7}\), \(5xy\) is an integer. Nonetheless, if both \(x\) and \(y\) are integers, then \(5xy\) is certainly an integer, thereby making \(10xy\) even.

(1) \(7 + x + y\) is an even integer.

Since \(7+x+y\) is even, then \(x+y\) must be odd. If \(x=1\) and \(y=2\), the answer will be YES. However, if \(x=1.3\) and \(y=1.7\), the answer will be NO. Not sufficient.

(2) \(x-y\) is an odd integer.

If \(x=1\) and \(y=2\), the answer will be YES. However, if \(x=1.3\) and \(y=0.3\), the answer will be NO. Not sufficient.

(1)+(2) From (1) we know that \(x+y=odd\) and from (2) we know that \(x-y=odd\). Adding these two equations gives \((x+y)+(x-y)=odd_1+odd_2\), which results in \(2x=even\). This implies that \(x=\frac{even}{2}\), which is an integer, and thus \(y\) is also an integer. Therefore, \(10xy=10*integer=even\). Sufficient.


Answer: C
---------------

Hi Bunuel, how do we know this is 10*x*y? While first attempting the question I thought x and y are the tens and ones place respectively.

If "10xy" were a four-digit number, it would have been explicitly mentioned. Without such clarification, "10xy" can only represent "10*x*y", as the multiplication sign (*) is typically omitted.
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