Need help with this data sufficiency problem

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targetthegmat: Newbie | Next Rank: 10 Posts; Posts: 3; Joined: Sun Feb 05, 2012 6:40 am; Thanked: 1 times

by targetthegmat » Sun Feb 26, 2012 6:42 am

If x and y are integers, what is the ratio of 2x to y?
8x3 = 27y3 (read x cube, y cube)
4x2 = 9y2 (read x square, y square)

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vijayrr007: Newbie | Next Rank: 10 Posts; Posts: 6; Joined: Sun Jun 05, 2011 10:51 am; Thanked: 3 times

by vijayrr007 » Sun Feb 26, 2012 9:15 am

I think the answer is A. we get 2x=3y from 1 which means the ratio is 3:1. for 2 since its a square we are not sure whether its positive or negative. it can be 2x=3y or -2x=3y.

targetthegmat wrote:If x and y are integers, what is the ratio of 2x to y?
8x3 = 27y3 (read x cube, y cube)
4x2 = 9y2 (read x square, y square)

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pemdas: Legendary Member; Posts: 1084; Joined: Fri Apr 15, 2011 2:33 pmFollowed by: 21 members; Thanked: 158 times

by pemdas » Sun Feb 26, 2012 6:28 pm

targetthegmat wrote:If x and y are integers, what is the ratio of 2x to y?
8x3 = 27y3 (read x cube, y cube)
4x2 = 9y2 (read x square, y square)

2x/y?
st(1) 8x^3=27y^3 implies (2x)^3=(3y)^3 or 2x=3y which is Sufficient to answer 2x/y, as 2x/3y=1 and 3*(2x/3y)=3

st(2) 4x^2=9y^2 implies (2x)^2=(3y)^2 or |2x|=|3y| Not Sufficient

a

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Anurag@Gurome: GMAT Instructor; Posts: 3835; Joined: Fri Apr 02, 2010 10:00 pmFollowed by: 523 members; Location: Milpitas, CA; Thanked: 1854 times; GMAT Score:770

by Anurag@Gurome » Mon Feb 27, 2012 2:21 am

targetthegmat wrote:If x and y are integers, what is the ratio of 2x to y?
8x3 = 27y3 (read x cube, y cube)
4x2 = 9y2 (read x square, y square)

(1) 8x^3 = 27y^3
(2x)^3 = (3y)^3
Taking cube root on both sides,
2x = 3y
2x : y = 3 : 1; SUFFICIENT.

(2) 4xÂ² = 9yÂ²
Taking square root on both sides,
Â±2x = 3y; NOT sufficient.

The correct answer is A.

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spideygirl: Newbie | Next Rank: 10 Posts; Posts: 1; Joined: Sat Apr 27, 2013 12:31 pm

by spideygirl » Sat Apr 27, 2013 12:34 pm

Hi, I have a question. I had picked (E) because I took the scenario of x and y being set to 0. Is it incorrect to use 0 as a value to plug in for x and y? Can we not take zero for both because x and y are two different variables?

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