Find all School-related info fast with the new School-Specific MBA Forum

 It is currently 19 Jun 2013, 08:36

# Data Sufficiency Question: MGMAT Cat 1 Problem #4

Author Message
TAGS:
Intern
Joined: 01 Oct 2010
Posts: 16
Followers: 0

Kudos [?]: 0 [0], given: 2

Data Sufficiency Question: MGMAT Cat 1 Problem #4 [#permalink]  29 Oct 2010, 08:28
00:00

Question Stats:

33% (00:00) correct 66% (01:38) wrong based on 6 sessions
I'm terrible with absolute values and need help understanding how to do this problem!

What is the value of y?

(1) 3|x2 – 4| = y – 2

(2) |3 – y| = 11

I understand that (1) alone is insufficient, but the explanation says that from (1) we can determine that y is greater than or equal to 2. Can someone please explain how this is deduced? Thanks!

*note that in (1) "x2" is meant to be x squared
[Reveal] Spoiler: OA
GMAT Club team member
Joined: 02 Sep 2009
Posts: 12116
Followers: 1879

Kudos [?]: 10122 [1] , given: 964

Re: Data Sufficiency Question: MGMAT Cat 1 Problem #4 [#permalink]  29 Oct 2010, 08:32
1
KUDOS
MLF44 wrote:
I understand that (1) alone is insufficient, but the explanation says that from (1) we can determine that y is greater than or equal to 2. Can someone please explain how this is deduced? Thanks!

*note that in (1) "x2" is meant to be x squared

What is the value of y?
(1) 3|x^2 -4| = y - 2
(2) |3 - y| = 11

(1) As we are asked to find the value of y, from this statement we can conclude only that y\geq{2}, as LHS is absolute value which is never negative, hence RHS als can not be negative. Not sufficient.

To elaborate more left hand side is some absolute value, absolute value is always non-negative: |some \ expression|\geq{0}, so RHS is also non-negative --> y-2\geq{0} --> y\geq{2}

(2) |3 - y| = 11:

y<3 --> 3-y=11 --> y=-8;
y\geq{3} --> -3+y=11 --> y=14.

Two values for y. Not sufficient.

(1)+(2) As from (1) y\geq{2}, then y=14. Sufficient.

For more on absolute values.
Theory: math-absolute-value-modulus-86462.html
Practice: inequality-and-absolute-value-questions-from-my-collection-86939.html

Hope it helps.
_________________
Intern
Joined: 01 Oct 2010
Posts: 16
Followers: 0

Kudos [?]: 0 [0], given: 2

Re: Data Sufficiency Question: MGMAT Cat 1 Problem #4 [#permalink]  29 Oct 2010, 08:37
DUH! Now I see it. Thank you so much!
Intern
Joined: 14 Sep 2010
Posts: 24
Followers: 1

Kudos [?]: 2 [0], given: 0

Equation problem Absolute values [#permalink]  29 Jan 2011, 03:50
What is the value of y?

(1) 3|x2 – 4| = y – 2

(2) |3 – y| = 11

My question is, that in the Manhattan Gmat guide, they always ask you to find solutions of the absolute value equation, and then PLUG both values in to the original equation. In case if one of those values dont match up, then that solution can be eliminated. If in either of the equations , we would find a value which could not work, then could we safely count that as sufficiency for that statement, or would we have to still assume that both are possible so not sufficient?

Thanks
GMAT Club team member
Joined: 02 Sep 2009
Posts: 12116
Followers: 1879

Kudos [?]: 10122 [0], given: 964

Re: Equation problem Absolute values [#permalink]  29 Jan 2011, 04:00
What is the value of y?

(1) 3|x2 – 4| = y – 2

(2) |3 – y| = 11

My question is, that in the Manhattan Gmat guide, they always ask you to find solutions of the absolute value equation, and then PLUG both values in to the original equation. In case if one of those values dont match up, then that solution can be eliminated. If in either of the equations , we would find a value which could not work, then could we safely count that as sufficiency for that statement, or would we have to still assume that both are possible so not sufficient?

Thanks

Merging similar topics. This question, along with other absolute value/inequality questions, is also discussed here: inequality-and-absolute-value-questions-from-my-collection-86939.html

As for your question: in DS questions, when we are asked to determine value of an unknown, statement is sufficient if it gives single numerical value of this unknown. So if you have two solutions for a variable out of which one is not valid for some reason then you are left with only one solution and thus the statement is sufficient (of course if you are asked to find the value of this variable).
_________________
Re: Equation problem Absolute values   [#permalink] 29 Jan 2011, 04:00
Similar topics Replies Last post
Similar
Topics:
Data Sufficiency problems 1 16 Oct 2005, 04:21
Problem Solving and Data Sufficiency 3 22 Jan 2008, 09:41
MGMAT's Number Properties Data Sufficiency Question 3 19 Dec 2010, 15:22
1 Data Sufficiency Q - MGMAT 3 28 Apr 2011, 06:01
Problems with Data Interpretation and Data Sufficiency 2 26 Jul 2012, 01:54
Display posts from previous: Sort by