Inequalities: If xy is less than 3, is x less than 1

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II: Master | Next Rank: 500 Posts; Posts: 400; Joined: Mon Dec 10, 2007 1:35 pm; Location: London, UK; Thanked: 19 times; GMAT Score:680

by II » Sun Mar 16, 2008 7:28 am

If xy is less than 3, is x less than 1

1) y is greater than 3
2) x is less than 3

thanks.

Last edited by II on Mon May 05, 2008 2:16 am, edited 1 time in total.

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Source: Beat The GMAT — Data Sufficiency | Sun Mar 16, 2008 7:28 am

camitava: Legendary Member; Posts: 645; Joined: Wed Sep 05, 2007 4:37 amFollowed by: 5 members; Location: India; Thanked: 34 times

Re: Inequalities ...

by camitava » Sun Mar 16, 2008 8:44 am

II wrote:If xy is less than 3, is x less than 1

1) y is greater than 3
2) x is less than 3

thanks.

II, the Qs is saying -
xy <3> 3 let say y = 4 and xy = 2 so x = 1/2
Again, y = 3.1 and xy = 2.9 so x = 0.935
So x <1> SUFF
stmt - 2, x < 3. But x can be between 1 and 3 or x can be less than 1.
So it is INSUFF.

So IMO A.

Correct me If I am wrong

Regards,

Amitava

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II: Master | Next Rank: 500 Posts; Posts: 400; Joined: Mon Dec 10, 2007 1:35 pm; Location: London, UK; Thanked: 19 times; GMAT Score:680

by II » Mon May 05, 2008 2:12 am

Is there another approach to solving this, apart from plugging in numbers ?

Thanks.
II

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zacharyz: Senior | Next Rank: 100 Posts; Posts: 68; Joined: Thu Feb 14, 2008 4:11 pm; Thanked: 7 times

by zacharyz » Mon May 05, 2008 1:34 pm

You can break it out into equations.

Given
x*y < 3 Need to know if x < 1
Therefore... let's look at various possible y
Positive y: x < 3 / y
y = 0 : x can be anything
Negative y: x > 3 / y (remember to flip the signs)

Statement 1:
y > 3. This is the positive case above. Therefore:
x < 3 / y

For all y greater than 3, 3 / y is going to be less than 1. Therefore:
x < 1 SUFFICIENT

Statement 2:
x < 3
Obviously this practically tells you that you do not know whether it is less than 1 or not. All you have to do is a logic check to confirm that there is no other information that can block 1 < x < 3 from being a real answer.
Nothing to our knowledge. There is some y that can be multiplied by 1 < x < 3 and be less than 3.
Therefore INSUFFICIENT

So the answer is (A)

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cramya: Legendary Member; Posts: 2467; Joined: Thu Aug 28, 2008 6:14 pmFollowed by: 11 members; Thanked: 331 times

by cramya » Mon Dec 15, 2008 10:03 pm

Is there another approach to solving this, apart from plugging in numbers ?

Stmt I

xy<3 (1)

y>3 i.e

3<y (2)

Add I and II

xy+3<3+y

xy-y<0
y(x-1) < 0

Either y<0 or x-1 < 0

Given y>3 so x-1<0 or x<1

SUFF

Another simple approach for Stmt I

xy<3
xy-3<0 (1)

3<y (2)

Add 1) and 2) (inqualities facing same direction)

xy-3+3<0+y
xy<y

Divide by y since we know y is positive(doesnt change the inequality )

x<1

SUFF

Stmt II

Pick numbers to prove insuff

A)

Last edited by cramya on Mon Dec 15, 2008 11:45 pm, edited 1 time in total.

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logitech: Legendary Member; Posts: 2134; Joined: Mon Oct 20, 2008 11:26 pmFollowed by: 25 members; Thanked: 237 times; GMAT Score:730

by logitech » Mon Dec 15, 2008 11:00 pm

cramya wrote:
Another simple approach for Stmt I

xy<3
xy-3<0 (1)

3<y (2)

Add 1) and 2) (inqualities facing same direction)

xy-3+3<0+y
xy<y

Divide by y since we know y is positive(doesnt change the inequality )

x<1

SUFF )

Sexy..

LGTCH
---------------------
"DON'T LET ANYONE STEAL YOUR DREAM!"

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ronniecoleman: Legendary Member; Posts: 546; Joined: Sun Nov 16, 2008 11:00 pm; Location: New Delhi , India; Thanked: 13 times

by ronniecoleman » Tue Dec 16, 2008 12:37 am

x*y < 3

1: y is positive

so x < 3/y

so x < 1

Suff...

Admission champion, Hauz khaz
011-27565856

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cramya: Legendary Member; Posts: 2467; Joined: Thu Aug 28, 2008 6:14 pmFollowed by: 11 members; Thanked: 331 times

by cramya » Tue Dec 16, 2008 6:51 pm

x*y < 3

1: y is positive

so x < 3/y

so x < 1

Suff...

Ronnie,
Good to see a nice approach for a change rather than a IMO.

Jus kidding!

I try not be blunt unlike my buddy Logitech!!!

Good luck with ur preps and keep up the good work!

Regards,
Cramya

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man man: Newbie | Next Rank: 10 Posts; Posts: 1; Joined: Tue Nov 18, 2008 9:06 pm

by man man » Thu Dec 18, 2008 7:44 am

X can be 2. x<3/y, and if y= 1.5, x=2.
So your condition doesn't work here.

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iamcste: Legendary Member; Posts: 940; Joined: Tue Aug 26, 2008 3:22 amFollowed by: 1 member; Thanked: 55 times

by iamcste » Thu Dec 18, 2008 8:06 am

man man wrote:X can be 2. x<3/y, and if y= 1.5, x=2.
So your condition doesn't work here.

In A, it is specifically mentioned that Y>3

so, Y canot be 1.5 for sure

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pbanavara: Master | Next Rank: 500 Posts; Posts: 279; Joined: Wed Sep 24, 2008 8:26 am; Location: Portland, OR; Thanked: 6 times

by pbanavara » Thu Dec 18, 2008 9:26 pm

xy < 3 Given

From 1 : y>3 , Let's say y=3 then to satisfy the above equation x<1 and since y>3 x has to be < 1. Sufficient

From 2 : x<3 doesn't mention anything about y and so x can take any value less than 3 : Insufficient

hence A. Loved the other approaches mentioned here.

- pradeep

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Jeff@TargetTestPrep: GMAT Instructor; Posts: 1462; Joined: Thu Apr 09, 2015 9:34 amFollowed by: 22 members; Location: New York, NY; Thanked: 39 times

by Jeff@TargetTestPrep » Mon Dec 11, 2017 4:13 pm

II wrote:If xy is less than 3, is x less than 1

1) y is greater than 3
2) x is less than 3

We are given that the product of x and y is less than 3 and must determine whether x < 1.

Statement One Alone:

y is greater than 3.

We are given that y is greater than 3. If x is greater than or equal to 1, then xy will be greater than 3. Therefore, in order for xy to be less than 3, x must be less than 1. Statement one alone is sufficient to answer the question.

Statement Two Alone:

x is less than 3.

The information in statement two is not sufficient to answer the question. For instance, if x = 2, and y = 1, then xy = 2(1) = 2. However, if x = 1/2 and y = 4, then xy = (1/2)(4) = 2. In the former case, x > 1; in the latter case, x < 1. Statement two alone is not sufficient to answer the question.

Answer: A

Jeffrey Miller
Head of GMAT Instruction
[email protected]

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