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took a little too long to solve this !!

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took a little too long to solve this !!

by vishubn » Tue Nov 11, 2008 8:17 pm
18. If x and y are nonzero integers, is(x/y) an integer?
(1) x is the product of 2 and some other integer.
(2) There is only one pair of positive integers whose product equals y.

I am little curious ! to know the approach :)

OA E
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by cramya » Tue Nov 11, 2008 8:22 pm
Vishu,

Stmt I)

tell us x is even No info about y INSUFF

Stmt II

tells us y is prime No info about x INSUFF

Taking 2 together still INSUFF

X/Y IS AN INTEGER IF PRIME y=2(still dont know if y is in fact 2 could be any other primes wiht may/may not be cases)

We can stop rught here and mark E)

Eg: 2*4 = 8 / 3 not an integer
2*6 / 3 = integer

INSUFF


Hope I have not missed something here!

E)
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Re: took a little too long to solve this !!

by logitech » Tue Nov 11, 2008 8:29 pm
vishubn wrote:18. If x and y are nonzero integers, is(x/y) an integer?
(1) x is the product of 2 and some other integer.
(2) There is only one pair of positive integers whose product equals y.

I am little curious ! to know the approach :)

OA E
Are you only a little bit curious ? Then I should only tell a little bit of my approach

1 and 2 both gives us separate info about X and Y so it is either C or E

1) X = 2K , where K is some other integer. So X is not equal to 4 :)
2) y = Prime ^ 2

1+2) it is not 4/4 - which was close ;-)

but it is 2X/Prime Prime = ? It can or not be an integer, Hence E

X=49
Y=49
SUF

X=3
Y=25
NOPE

TATAM!!
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by cramya » Tue Nov 11, 2008 8:56 pm
2) y = Prime ^ 2

I am not so sure on the y=prime^2 part

1 pair of positive integers in the sense (1,2) or (2,1) ; (1,3) or (3,1)

Regards,
Cramya
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by vishubn » Tue Nov 11, 2008 9:25 pm
yaaa ! was concerned ! that i took around 3 mins ! looked eassy when solving but realized the time !!

Thanks u guys

Vishu

ps. i know the well know quote in the forum about the 2:00 and 2:30 mins
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by logitech » Tue Nov 11, 2008 9:26 pm
cramya wrote:
2) y = Prime ^ 2

I am not so sure on the y=prime^2 part

1 pair of positive integers in the sense (1,2) or (2,1) ; (1,3) or (3,1)

Regards,
Cramya
You are right cramya. I think the wording cannot be translated into what I came up with.

How about y=prime ? ( Nx1)
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by cramya » Tue Nov 11, 2008 9:37 pm
You are right cramya. I think the wording cannot be translated into what I came up with.

How about y=prime ? ( Nx1)

Yep that works!
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by Stuart@KaplanGMAT » Wed Nov 12, 2008 1:24 am
Just a quick note:

"There is only one pair of positive integers whose product equals y."

Y could be prime, but y could also equal 1, since only one pair of positive integers (1*1) equals 1.

Without the word "distinct" in the statement, we can't assume that the integers must be different.

(E) is, of course, still the correct answer.
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by logitech » Wed Nov 12, 2008 1:33 am
Thanks Stuart.
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by cramya » Wed Nov 12, 2008 5:25 am
Thanks Stuart!
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