Author 
Message 
TAGS:

Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 44319

Question Stats:
69% (01:57) correct 31% (00:38) wrong based on 81 sessions
HideShow timer Statistics



Math Expert
Joined: 02 Sep 2009
Posts: 44319

Re M2612 [#permalink]
Show Tags
16 Sep 2014, 01:25



Current Student
Joined: 06 Mar 2014
Posts: 267
Location: India
GMAT Date: 04302015

Re: M2612 [#permalink]
Show Tags
16 Sep 2014, 10:42
1
This post received KUDOS
Bunuel wrote: Official Solution:
If \(3 \lt x \lt 5\) and \(7 \lt y \lt 9\), which of the following represents the range of all possible values of \(yx\)?
A. \(4 \lt yx \lt 4\) B. \(2 \lt yx \lt 4\) C. \(12 \lt yx \lt 4\) D. \(12 \lt yx \lt 12\) E. \(4 \lt yx \lt 12\)
To get max value of \(yx\) take max value of \(y\) and min value of \(x\): \(9(3)=12\); To get min value of \(yx\) take min value of \(y\) and max value of \(x\): \(7(5)=12\); Hence, the range of all possible values of \(yx\) is \(12 \lt yx \lt 12\).
Answer: D This question is good but it would be interesting to see a question with the same guidelines as to find the range of values but with the variables x/y or both with inclusive numbers like 3<=x<5 and 7<y<=9. Also if possible, kindly suggest similar problems.



Math Expert
Joined: 02 Sep 2009
Posts: 44319

Re: M2612 [#permalink]
Show Tags
16 Sep 2014, 14:32
earnit wrote: Bunuel wrote: Official Solution:
If \(3 \lt x \lt 5\) and \(7 \lt y \lt 9\), which of the following represents the range of all possible values of \(yx\)?
A. \(4 \lt yx \lt 4\) B. \(2 \lt yx \lt 4\) C. \(12 \lt yx \lt 4\) D. \(12 \lt yx \lt 12\) E. \(4 \lt yx \lt 12\)
To get max value of \(yx\) take max value of \(y\) and min value of \(x\): \(9(3)=12\); To get min value of \(yx\) take min value of \(y\) and max value of \(x\): \(7(5)=12\); Hence, the range of all possible values of \(yx\) is \(12 \lt yx \lt 12\).
Answer: D This question is good but it would be interesting to see a question with the same guidelines as to find the range of values but with the variables x/y or both with inclusive numbers like 3<=x<5 and 7<y<=9. Also if possible, kindly suggest similar problems. Here is a similar questions with equal signs: if2x2and3y8whichofthefollowingrepresentsthe73539.html
_________________
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



Current Student
Joined: 12 Aug 2015
Posts: 296
Concentration: General Management, Operations
GMAT 1: 640 Q40 V37 GMAT 2: 650 Q43 V36 GMAT 3: 600 Q47 V27
GPA: 3.3
WE: Management Consulting (Consulting)

1
This post was BOOKMARKED
Hi another approach: sum up the 2 inequalities. but mind that the inequalities for such operaton should be looking the same way. since we need to find yx, we need to figure out how to transform the xinequality into the required form, i.e. x: 1. multiply by (1): we get +3>x>5 (remember to flip direction when * 1) 2. still is not looking the same way, therefore: 5<x<3 is just the same expression of the number line fragment 3. sumup: 7 < y <9 5 <x <3  75 < yx < 9+3 12 < yx< 12 ANSWER D
_________________
KUDO me plenty



Intern
Joined: 24 Nov 2015
Posts: 2

Re M2612 [#permalink]
Show Tags
01 Jan 2016, 21:01
1
This post received KUDOS
The questions states that the values are less than or greater than. but the answer explanation uses values that are greater than or EQUAL TO!! The explanation uses values that are not in the range of values given in the question



Current Student
Joined: 17 Oct 2015
Posts: 30
Concentration: Technology, Leadership

Re: M2612 [#permalink]
Show Tags
03 Mar 2016, 17:35
The same for me.. Is the OE wrong? weiling476 wrote: The questions states that the values are less than or greater than. but the answer explanation uses values that are greater than or EQUAL TO!! The explanation uses values that are not in the range of values given in the question



Math Expert
Joined: 02 Sep 2009
Posts: 44319

Re: M2612 [#permalink]
Show Tags
07 Mar 2016, 10:41



Intern
Joined: 26 Mar 2016
Posts: 1

Re M2612 [#permalink]
Show Tags
06 Apr 2016, 01:29
I don't agree with the explanation. If x is less than 9 then maximum value of x is 8. similarly for Y. kindly explain why maximum value for x is 9.



Math Expert
Joined: 02 Sep 2009
Posts: 44319

Re: M2612 [#permalink]
Show Tags
06 Apr 2016, 01:38



Intern
Joined: 28 Dec 2016
Posts: 43
Location: United States
WE: Analyst (Consumer Products)

Bunuel,
I'm not doubting the question itself, but when other people raised issues about the explanation, i think it's reasonable to doubt why the maximum VALUE of y is 9, and minimum VALUE of x is 3. Your wording is totally misguiding. You should say the maximum RANGE of y, rather than the value. The maximum value in this case is not 9, it's 8.99. Since the question is saying that the range is <>, not <=,>=.



Math Expert
Joined: 02 Sep 2009
Posts: 44319

Re: M2612 [#permalink]
Show Tags
08 Jan 2017, 05:49
conneryeon001 wrote: Bunuel,
I'm not doubting the question itself, but when other people raised issues about the explanation, i think it's reasonable to doubt why the maximum VALUE of y is 9, and minimum VALUE of x is 3. Your wording is totally misguiding. You should say the maximum RANGE of y, rather than the value. The maximum value in this case is not 9, it's 8.99. Since the question is saying that the range is <>, not <=,>=. The question and the solution are absolutely correct. I think your doubt is addressed here: m26184451.html#p1655617Hope it helps.
_________________
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: 26 Sep 2016
Posts: 23

Re: M2612 [#permalink]
Show Tags
21 Apr 2017, 01:36
I think a much simpler way to solve this problem is to simply subtract two inequlities, according to the inequalities subtraction rules: (7<y<9)(5>x>3) <last inequality simply reversed. And we get the same answer 12<yx<12



Manager
Joined: 23 Jun 2016
Posts: 137

Re: M2612 [#permalink]
Show Tags
09 Nov 2017, 19:12
(1) 3<x<5 (2) 7<y<9
I made a mistake and subtracted (1) from (2) (since signs are similar in two statements) giving 4 < (yx) < 4
I agree with the OE but can someone explain if the above allowed and if yes what information does it convey?



Math Expert
Joined: 02 Aug 2009
Posts: 5721

Re: M2612 [#permalink]
Show Tags
09 Nov 2017, 19:46
sevenplusplus wrote: (1) 3<x<5 (2) 7<y<9
I made a mistake and subtracted (1) from (2) (since signs are similar in two statements) giving 4 < (yx) < 4
I agree with the OE but can someone explain if the above allowed and if yes what information does it convey? No, it is wrong and you can simply test it with numbers.. (1) 3<x<5 ......let x be the lowest possible 2.99999 (2) 7<y<9 ...... let y be the MAX, so 8.99999 yx = 8.99999(2.99999) = 10 and 10 is not in the range 4<yx<4 you can ofcourse ADD the equations.. (1) 3<x<5 (2) 7<y<9 so 3+(7)<x+y<5+9......10<x+y<14 so to sum it all 1) if you are adding, take highest values and add them and for lower range add lowest values and add them 2) If you are subtracting, take highest of one and lowest of other
_________________
Absolute modulus :http://gmatclub.com/forum/absolutemodulusabetterunderstanding210849.html#p1622372 Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html
GMAT online Tutor



Manager
Joined: 23 Jun 2016
Posts: 137

Re: M2612 [#permalink]
Show Tags
11 Nov 2017, 11:17
chetan2u wrote: sevenplusplus wrote: (1) 3<x<5 (2) 7<y<9
I made a mistake and subtracted (1) from (2) (since signs are similar in two statements) giving 4 < (yx) < 4
I agree with the OE but can someone explain if the above allowed and if yes what information does it convey? No, it is wrong and you can simply test it with numbers.. (1) 3<x<5 ......let x be the lowest possible 2.99999 (2) 7<y<9 ...... let y be the MAX, so 8.99999 yx = 8.99999(2.99999) = 10 and 10 is not in the range 4<yx<4 you can ofcourse ADD the equations.. (1) 3<x<5 (2) 7<y<9 so 3+(7)<x+y<5+9......10<x+y<14 so to sum it all 1) if you are adding, take highest values and add them and for lower range add lowest values and add them 2) If you are subtracting, take highest of one and lowest of other Thanks a ton. Sent from my iPhone using GMAT Club Forum mobile app



Intern
Joined: 18 Mar 2015
Posts: 15

Re: M2612 [#permalink]
Show Tags
17 Dec 2017, 08:17
hi bunuel :
max value of yx is 8 (2) and not 9 3 bcoz the sign used is < and > and not <= or >=
similar for min value



Math Expert
Joined: 02 Sep 2009
Posts: 44319

Re: M2612 [#permalink]
Show Tags
17 Dec 2017, 09:22










