Author 
Message 
TAGS:

Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 43810

Re: What is the value of y? [#permalink]
Show Tags
25 Sep 2013, 02:33



Intern
Joined: 30 Apr 2010
Posts: 21

Re: What is the value of y? [#permalink]
Show Tags
16 Oct 2013, 05:34
What is the value of y?
(1) 3x^2 – 4 = y – 2 (2) 3 – y = 11
(1) 3x^2  4 = y  2
the LHS is an absolute value so RHS has to be positive or zero: y  2 >=0. Multiple values for y so not sufficient.
(2) 3 – y = 11
y can either be 8 or 14 3  (8) = 11 = 11 3  14 = 11 = 11 two possible values for y so not sufficient
(1) + (2)
from (1) we know that y >= 2 from (2) we know that y = 8 or y = 11 therefore y = 11
Answer: C



Intern
Status: preparing for the GMAT
Joined: 16 Jul 2013
Posts: 37
Concentration: Technology, Entrepreneurship
GMAT Date: 10152013
GPA: 3.53

Re: What is the value of y? [#permalink]
Show Tags
28 Oct 2013, 08:10
Bunuel wrote: What is the value of y?
(1) \(3x^24=y2\). Now, since 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 cannot be negative. Not sufficient.
(2) \(3  y = 11\):
\(y<3\) > \(3y=11\) > \(y=8\); \(y\geq{3}\) > \(3+y=11\) > \(y=14\).
Two values for \(y\). Not sufficient.
(1)+(2) Since from (1) \(y\geq{2}\), then from (2) \(y=14\). Sufficient.
Answer: C.
Hope it's clear. Hi Bunuel, in the second statement, you solved the inequality and got 8 and 14 which satisfy the inequality if you plug them. but, what about if you get two answers, and one satisfies the inequality and one doesn't. for example x+3 = 4x3, how do you go about that?
_________________
لا الله الا الله, محمد رسول الله
You never fail until you stop trying ,,,



Senior Manager
Joined: 07 Apr 2012
Posts: 441

Re: What is the value of y? [#permalink]
Show Tags
04 Nov 2013, 14:25
Bunuel wrote: What is the value of y?
(1) \(3x^24=y2\). Now, since 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 cannot be negative. Not sufficient.
(2) \(3  y = 11\):
\(y<3\) > \(3y=11\) > \(y=8\); \(y\geq{3}\) > \(3+y=11\) > \(y=14\).
Two values for \(y\). Not sufficient.
(1)+(2) Since from (1) \(y\geq{2}\), then from (2) \(y=14\). Sufficient.
Answer: C.
Hope it's clear. I have a general question... I went ahead and solved the equation in st. 1 and got that x = sqrt(8)... Now, if we were told that both x and y were integers, than does that mean that both statements were not sufficient? Would have it affected our final result? Because st.1 doesn't really just say that y>= 2 right? It actually gives y a value.....?



Math Expert
Joined: 02 Sep 2009
Posts: 43810

Re: What is the value of y? [#permalink]
Show Tags
05 Nov 2013, 06:20
ronr34 wrote: Bunuel wrote: What is the value of y?
(1) \(3x^24=y2\). Now, since 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 cannot be negative. Not sufficient.
(2) \(3  y = 11\):
\(y<3\) > \(3y=11\) > \(y=8\); \(y\geq{3}\) > \(3+y=11\) > \(y=14\).
Two values for \(y\). Not sufficient.
(1)+(2) Since from (1) \(y\geq{2}\), then from (2) \(y=14\). Sufficient.
Answer: C.
Hope it's clear. I have a general question... I went ahead and solved the equation in st. 1 and got that x = sqrt(8)... Now, if we were told that both x and y were integers, than does that mean that both statements were not sufficient? Would have it affected our final result? Because st.1 doesn't really just say that y>= 2 right? It actually gives y a value.....? How did you get from (1) that \(x=\sqrt{8}\)? That's not correct. You cannot solve \(3x^24=y2\). Next, yes y is some number but whatever number it is from \(3x^24=y2\) it follows that it's more than or equal to 2.
_________________
New to the Math Forum? Please read this: Ultimate GMAT Quantitative Megathread  All You Need for Quant  PLEASE READ AND FOLLOW: 12 Rules for Posting!!! Resources: GMAT Math Book  Triangles  Polygons  Coordinate Geometry  Factorials  Circles  Number Theory  Remainders; 8. Overlapping Sets  PDF of Math Book; 10. Remainders  GMAT Prep Software Analysis  SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS)  Tricky questions from previous years.
Collection of Questions: PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.
What are GMAT Club Tests? Extrahard Quant Tests with Brilliant Analytics



Intern
Joined: 13 Apr 2014
Posts: 14

Re: What is the value of y? [#permalink]
Show Tags
17 Apr 2014, 01:00
Bunuel, I understand from statement 1 we get y>=2 , but when we combine both statements together we get y>=2 and y=14. Now how can we just assume y to be 14, because y can also take the value of 2 right . I chose E on this basis . tnx dear
_________________
http://www.gmatacademy.ir best for iranian



Manager
Joined: 20 Dec 2013
Posts: 129

Re: What is the value of y? [#permalink]
Show Tags
17 Apr 2014, 01:42
dvinoth86 wrote: What is the value of y?
(1) 3x^2 – 4 = y – 2 (2) 3 – y = 11 Statement I is insufficient x will take multiple values and so will y.The only takeaway from this option is that y = 3(+ve) + 2 hence y is a positive number Statement II is insufficient: 3  y = 11 y = 8 3  y = 11 y = 14 Combining is sufficient. First statement says that y is a positive number and second statement says that y is either 11 or 14 hence y is equal to 14.
_________________
76000 Subscribers, 7 million minutes of learning delivered and 5.6 million video views
Perfect Scores http://perfectscores.org http://www.youtube.com/perfectscores



Math Expert
Joined: 02 Sep 2009
Posts: 43810

Re: What is the value of y? [#permalink]
Show Tags
17 Apr 2014, 01:49



Manager
Joined: 07 Apr 2014
Posts: 132

Re: What is the value of y? [#permalink]
Show Tags
07 Sep 2014, 01:51
dvinoth86 wrote: What is the value of y?
(1) 3x^2 – 4 = y – 2 (2) 3 – y = 11 1. from one we could conclude either y is greater than or equal to 2 as x^2  4 always greater than ive values. but we cant determine the values hence Insuff. 2. y could be 8 or 14 , two values .. In sufff. combining from one , y is greater than or equal to 2 & from two y= 8 or 14 .. y should be 14. Hence C



Manager
Joined: 30 May 2012
Posts: 217
Location: United States (TX)
Concentration: Finance, Marketing
GPA: 3.3
WE: Information Technology (Consulting)

Re: What is the value of y? [#permalink]
Show Tags
05 Nov 2014, 04:57
Quick couple of questions around Absolute value and inequalities 1.When 4\(x + 1/2\) = 18 can become + (x + 1/2) = 4.5 or –(x + 1/2) = 4.5, why can't 3\(x^2\) – 4 = y – 2 become (\(x^2\) – 4)= (y – 2)/3 or (\(x^2\) – 4) = (y – 2)/3 ? 2. What happens to the inequality when you take the square root on both the sides? For e.g. \(x^2\) \(<=\)1. Also, please let me know if there are any specific rules when squaring on both sides? Thanks in advance



Math Expert
Joined: 02 Sep 2009
Posts: 43810

Re: What is the value of y? [#permalink]
Show Tags
05 Nov 2014, 05:11



Manager
Joined: 30 May 2012
Posts: 217
Location: United States (TX)
Concentration: Finance, Marketing
GPA: 3.3
WE: Information Technology (Consulting)

Re: What is the value of y? [#permalink]
Show Tags
05 Nov 2014, 06:47
Bunuel wrote: 1. We could, but this is no help in finding the value of y. Thank you. For a few hours I was searching all over fanatically to verify if my fundamental understanding of modulus theory is flawed. Now, I know what else I could do when a modulus operator is present. And thanks also for the linky, I will check it out now.



Intern
Joined: 16 Aug 2014
Posts: 9

Re: What is the value of y? [#permalink]
Show Tags
21 Nov 2014, 08:38
Hello Bunuel Thanks for your posts! Btw, Why couldn't 'y' take both the values ( 8 & 14) as per statement 2?! Iam unable to paste links;I could find sites like 'sosmath' where both the values are shown as solutions



Math Expert
Joined: 02 Sep 2009
Posts: 43810

Re: What is the value of y? [#permalink]
Show Tags
21 Nov 2014, 08:52



Intern
Joined: 16 Aug 2014
Posts: 9

Re: What is the value of y? [#permalink]
Show Tags
21 Nov 2014, 19:23
Bunuel wrote: musejoy wrote: Hello Bunuel Thanks for your posts! Btw, Why couldn't 'y' take both the values ( 8 & 14) as per statement 2?! Iam unable to paste links;I could find sites like 'sosmath' where both the values are shown as solutions y could be either 8 or 14. What is confusing there? So,if 'y' can take both values, that would mean statement 2 is right kno? Linear absolute value equations can have 2 values as solutions, am i right please?



Manager
Joined: 21 Jan 2014
Posts: 62
WE: General Management (NonProfit and Government)

What is the value of y? [#permalink]
Show Tags
22 Nov 2014, 03:05
1) 3x^2 – 4 = y – 2 : Above equation indicates that y is positive. No definite value of y so INSUFFICIENT.
2) 3 – y = 11 Square both sides and solving this equation for y 9+y^26y=121 so y=14 or 4 No definite values of y .INSUFFICIENT.
Combining both statements, once can say y=14 is definite answer.
Answer is C



Math Expert
Joined: 02 Sep 2009
Posts: 43810

Re: What is the value of y? [#permalink]
Show Tags
22 Nov 2014, 06:23
musejoy wrote: Bunuel wrote: musejoy wrote: Hello Bunuel Thanks for your posts! Btw, Why couldn't 'y' take both the values ( 8 & 14) as per statement 2?! Iam unable to paste links;I could find sites like 'sosmath' where both the values are shown as solutions y could be either 8 or 14. What is confusing there? So,if 'y' can take both values, that would mean statement 2 is right kno? Linear absolute value equations can have 2 values as solutions, am i right please? No. When a DS question asks about the value of some variable, then the statement(s) is sufficient ONLY if you can get the single numerical value of this variable. So, the second statement is NOT sufficient because we can two possible values of y, not one. Hope it's clear.
_________________
New to the Math Forum? Please read this: Ultimate GMAT Quantitative Megathread  All You Need for Quant  PLEASE READ AND FOLLOW: 12 Rules for Posting!!! Resources: GMAT Math Book  Triangles  Polygons  Coordinate Geometry  Factorials  Circles  Number Theory  Remainders; 8. Overlapping Sets  PDF of Math Book; 10. Remainders  GMAT Prep Software Analysis  SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS)  Tricky questions from previous years.
Collection of Questions: PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.
What are GMAT Club Tests? Extrahard Quant Tests with Brilliant Analytics



Intern
Joined: 23 Sep 2014
Posts: 37
Location: India
Concentration: Marketing, Finance

Re: What is the value of y? [#permalink]
Show Tags
01 Sep 2015, 00:59
Bunuel wrote: davidfrank wrote: Bunuel wrote: What is the value of y?
(1) \(3x^24=y2\). Now, since 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 cannot be negative. Not sufficient.
(2) \(3  y = 11\):
\(y<3\) > \(3y=11\) > \(y=8\); \(y\geq{3}\) > \(3+y=11\) > \(y=14\).
Two values for \(y\). Not sufficient.
(1)+(2) Since from (1) \(y\geq{2}\), then from (2) \(y=14\). Sufficient.
Answer: C.
Hope it's clear. Hi, Can I solve statement 1 like this: 3x^24=y2 Now since this is an absolute value I would 1st solve for x x^24=0 x2=4 and x=+/2 now if I substituent the value of x in the above expression If x= +2 3x^24=y2 3(2)^24=y2 30=y2 therefore y=2 now if x=2 3x^24=y2 3(2)^24=y2 30=y2 and therefore y=2 In both the cases I will get the same value for Y. Can someone please explain what is wrong with this approach. We don't know whether x^24=0, thus all your further steps are based on that false assumption. If we knew that x^24=0, then x^24=0=y2 > y2=0 > y=2. Also, you can notice that your approach is not correct from the fact that on the GMAT, two data sufficiency statements always provide TRUE information and these statements never contradict each other. From (2) we have that y is 8 or 14, and if from (1) you get that y is 2 it would mean that the statements clearly contradict. Does this make sense? Why cannot we solve the 1st as : 3x^24 =y2 x^24 = (y2)/3 x^2= (y+10)/3 (1) and considering the negative sign i.e x^24=(y2)/3 x^2= (y+14)/3 (2) and then equating 1 and 2 we will get y = 2 What is wrong with this approach??



Math Expert
Joined: 02 Sep 2009
Posts: 43810

Re: What is the value of y? [#permalink]
Show Tags
01 Sep 2015, 03:41
believer700 wrote: Bunuel wrote: davidfrank wrote: Hi,
Can I solve statement 1 like this:
3x^24=y2
Now since this is an absolute value
I would 1st solve for x
x^24=0 x2=4 and x=+/2 now if I substituent the value of x in the above expression If x= +2 3x^24=y2 3(2)^24=y2 30=y2 therefore y=2
now if x=2 3x^24=y2 3(2)^24=y2 30=y2 and therefore y=2
In both the cases I will get the same value for Y.
Can someone please explain what is wrong with this approach. We don't know whether x^24=0, thus all your further steps are based on that false assumption. If we knew that x^24=0, then x^24=0=y2 > y2=0 > y=2. Also, you can notice that your approach is not correct from the fact that on the GMAT, two data sufficiency statements always provide TRUE information and these statements never contradict each other. From (2) we have that y is 8 or 14, and if from (1) you get that y is 2 it would mean that the statements clearly contradict. Does this make sense? Why cannot we solve the 1st as : 3x^24 =y2 x^24 = (y2)/3 x^2= (y+10)/3 (1) and considering the negative sign i.e x^24=(y2)/3 x^2= (y+14)/3 (2) and then equating 1 and 2 we will get y = 2 What is wrong with this approach?? Those are 2 separate cases: x^2  4 = x^2  4, when x^2  4 > 0 and x^2  4 = (x^2  4), when x^2  4 < 0.
_________________
New to the Math Forum? Please read this: Ultimate GMAT Quantitative Megathread  All You Need for Quant  PLEASE READ AND FOLLOW: 12 Rules for Posting!!! Resources: GMAT Math Book  Triangles  Polygons  Coordinate Geometry  Factorials  Circles  Number Theory  Remainders; 8. Overlapping Sets  PDF of Math Book; 10. Remainders  GMAT Prep Software Analysis  SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS)  Tricky questions from previous years.
Collection of Questions: PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.
What are GMAT Club Tests? Extrahard Quant Tests with Brilliant Analytics



Intern
Joined: 11 Jan 2016
Posts: 1
Location: India
Schools: HBS '19, Kellogg '19 (D), Booth '19, Sloan '19, Haas '19, Tuck '19, Stern '19, Yale '19, Duke '19, Darden '19, KenanFlagler '19, McDonough '19 (WL), ISB '18 (A), Owen '19, Boston U '19 (A)
GPA: 3.5

What is the value of y? [#permalink]
Show Tags
26 Apr 2016, 02:12
1
This post was BOOKMARKED
Bunuel wrote: What is the value of y?
(1) \(3x^24=y2\). Now, since 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 cannot be negative. Not sufficient.
(2) \(3  y = 11\):
\(y<3\) > \(3y=11\) > \(y=8\); \(y\geq{3}\) > \(3+y=11\) > \(y=14\).
Two values for \(y\). Not sufficient.
(1)+(2) Since from (1) \(y\geq{2}\), then from (2) \(y=14\). Sufficient.
Answer: C.
Hope it's clear. what if y is between 2 and 3? In that case we will have two values of y. Could you please clarify?




What is the value of y?
[#permalink]
26 Apr 2016, 02:12



Go to page
Previous
1 2 3
Next
[ 49 posts ]



