If x and y are different integers, both divisible by 5, then which is

Question

If x and y are different integers, both divisible by 5, then which is not necessarily true?

(A) x^2 + y^2 is divisible by 5

(B) x - y is divisible by 5

(C) xy is divisible by 5

(D) x + y is divisible by 5

(E) x + y is divisible by 10

Kurtosis · Answer

x = 5k_1
y = 5k_2

A) x^2 + y^2 = 25(K_1^2 + K_2^2) --> Divisible by 5
B) x - y = 5(K_1 - K_2) --> Divisible by 5
C) xy = 25(K_1*K_2) --> Divisible by 5
D) x + y = 5(K_1 + K_2) --> Divisible by 5
 E) x + y = 5(K_1 + K_2) --> Not divisible by 10 always

Answer: E

Abhishek009 · Answer

The best way to solve this problem is plugging in some values of x and y

Let x = 5 and y = 10

(A) x^2 + y^2 is 125 (25+100) which is divisible by 5

(B) x - y is -5 ( 5 - 10 ) which is divisible by 5

(C) xy is 50 (5*10) which is divisible by 5

(D) x + y is 15 ( 5 + 10 ) which is divisible by 5

(D) x + y is 15 ( 5 + 10 ) which is not divisible by 10

Hence IMHO (E)

EMPOWERgmatRichC · Answer

Hi All,

This question can be solved rather easily by TESTing VALUES (the approach that Abhishek009 used). The prompt never states that X and Y are positive though, so you don't have to use two different positive multiples of 5. You COULD use...

X = 0
Y = 5

That would make the calculations even easier/faster and still provide the correct answer to the question.

Final Answer:  E

GMAT assassins aren't born, they're made,
Rich

stonecold · Answer

Here we can choose 5,10 and 5,15 as the possible cases
and apart of E all satisfy the requirement
hence E

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If x and y are different integers, both divisible by 5, then which is

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If x and y are different integers, both divisible by 5, then which is

Prep Toolkit

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