Is X < Y ?

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adi: Junior | Next Rank: 30 Posts; Posts: 23; Joined: Mon Jan 07, 2008 12:55 pm; Location: Frisco, Texas

Is X < Y ?

by adi » Sat Mar 08, 2008 2:33 pm

Is x<y ?

(1) 2x < 3y
(2) xy > 0

I really thought this one would be C (both would answer the question), but the key says it's E.

Any thoughts as to why?

Last edited by adi on Sat Mar 08, 2008 5:05 pm, edited 1 time in total.

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Source: Beat The GMAT — Data Sufficiency | Sat Mar 08, 2008 2:33 pm

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Re: Is X < Y ?

by Stuart@KaplanGMAT » Sat Mar 08, 2008 3:38 pm

adi wrote:Is x<y ?

(1) 2x <3y> 0

I really thought this one would be C (both would answer the question), but the key says it's E.

Any thoughts as to why?

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adi: Junior | Next Rank: 30 Posts; Posts: 23; Joined: Mon Jan 07, 2008 12:55 pm; Location: Frisco, Texas

by adi » Sat Mar 08, 2008 5:06 pm

Thanks for pointing out the error.

I have edited my initial post. 8)

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Stuart@KaplanGMAT: GMAT Instructor; Posts: 3225; Joined: Tue Jan 08, 2008 2:40 pm; Location: Toronto; Thanked: 1710 times; Followed by:614 members; GMAT Score:800

Re: Is X < Y ?

by Stuart@KaplanGMAT » Sat Mar 08, 2008 5:29 pm

adi wrote:Is x<y ?

(1) 2x < 3y
(2) xy > 0

I really thought this one would be C (both would answer the question), but the key says it's E.

Any thoughts as to why?

Whenever inequalities are involved, we want to focus on the signs of the variables.

(1) 2x < 3y

or

x < (3/2)y

Does this tell us if x is less than y?

Nope, we could pick x=1 and y=50 to get a "yes" answer or we could pick x = 1.1 and y = 1 to get "no" answer: insufficient.

(2) xy > 0

This tells us that x and y are both positive or both negative, but nothing about the values: insufficient.

When we combine the statements, we can still get both a "yes" and a "no", since both sets of numbers from statement (1) could still be used.

Choose (E).