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If x and y are positive integers is y odd? [#permalink]
 04 Mar 2012, 23:42
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68% (01:31) wrong based on 64 sessions
If x and y are positive integers is y odd? (1) (y+2)!/x! = odd (2) (y+2)!/x! is greater than 2
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Re: If x and y are positive integers is y odd? [#permalink]
05 Mar 2012, 00:37
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If x and y are positive integers is y odd?(1) (y+2)!/x! = odd. Notice that \frac{(y+2)!}{x!}=odd can happen only in two cases: A. (y+2)!=x! in this case \frac{(y+2)!}{x!}=1=odd. For this case y can be even: y=2=even and x=4: \frac{(y+2)!}{x!}=\frac{24}{24}=1=odd; B. y=odd and x=y+1, in this case \frac{(y+2)!}{(y+1)!}=y+2=odd. For example, y=1=odd and x=y+1=2: \frac{(y+2)!}{x!}=\frac{3!}{2!}=3=odd (basically all the cases like: 3!/2!, 5!/4!, 7!/6!, ... --> y+2=odd, 3, 5, 7, ... --> y=odd, 1, 3, 5, ...). Not sufficient. (2) (y+2)!/x! is greater than 2. Clearly insufficient: consider y=1=odd and x=2 OR y=2=even and x=1. (1)+(2) From (2) we cannot have case A, hence we have case B, which means y=odd. Sufficient. Answer: C. Hope it's clear.
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if x and y are positive integers, is y odd? [#permalink]
24 Jun 2012, 14:37
if x and y are positive integers, is y odd?
1.) (y+2)!/x! is an odd integer
2.) (y+2)!/x! is greater than 2
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Re: If x and y are positive integers is y odd? [#permalink]
24 Sep 2012, 23:17
very good explanation
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Tricky DS Question [#permalink]
25 Sep 2012, 06:51
If x and y are positive integers, is y odd?
(1) (y+2)!/x! is an odd integer.
(2) (y+2)!/x! is greater than 2.
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Re: Tricky DS Question [#permalink]
25 Sep 2012, 06:55
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Re: Tricky DS Question
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25 Sep 2012, 06:55
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