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integer..

by vivid007 » Mon Jan 21, 2008 10:09 am
If x+y is an integer, is y an integer?

1) x-y is an integer.
2) x+2y is an integer.



The answer is B. but couldn't find my way out of this maze.
Please give me a way~!!
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Source: — Data Sufficiency |
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by sankruth » Mon Jan 21, 2008 10:37 am
St 1
x - y is Integer

x = 1.5; y = 0.5

x+y = 2 (Int)
x-y = 1 (Int)

But y not Integer. So St1 INSUFF

St 2
x + 2y = (x + y) + y

(Integer + Non Integer) CANNOT add up to an Integer. Since (x + y) is Integer, s y must be an Integer.

SUFF, Hence B
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by preciousrain7 » Wed Jan 23, 2008 11:32 am
sankruth wrote:St 1
x - y is Integer

x = 1.5; y = 0.5

x+y = 2 (Int)
x-y = 1 (Int)

But y not Integer. So St1 INSUFF

St 2
x + 2y = (x + y) + y

(Integer + Non Integer) CANNOT add up to an Integer. Since (x + y) is Integer, s y must be an Integer.

SUFF, Hence B
How do you know that X+Y is an integer?

Using your equation:
(X+Y)+Y: what if X=1.5 and Y=.5, then the answer will end up being an integer...
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by sankruth » Wed Jan 23, 2008 11:35 am
Question stem says (x + y) is an Integer.
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by preciousrain7 » Wed Jan 23, 2008 12:03 pm
sankruth wrote:Question stem says (x + y) is an Integer.
haha oops thanks!
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