Author 
Message 
TAGS:

Hide Tags

Director
Joined: 25 Oct 2008
Posts: 561
Location: Kolkata,India

The value of cube root of (89) is: [#permalink]
Show Tags
03 Nov 2009, 18:23
3
This post received KUDOS
41
This post was BOOKMARKED
Question Stats:
44% (00:55) correct 56% (00:42) wrong based on 993 sessions
HideShow timer Statistics
The value of cube root of (89) is: A. Between 9 and 10 B. Between 8 and 9 C. Between 4 and 5 D. Between 3 and 4 E. Undefined
Official Answer and Stats are available only to registered users. Register/ Login.
_________________
http://gmatclub.com/forum/countdownbeginshasended8548340.html#p649902



VP
Joined: 05 Mar 2008
Posts: 1428

Re: cube root of (89) [#permalink]
Show Tags
03 Nov 2009, 18:43
tejal777 wrote: The value of cube root of (89) is..? Between 9 and 10 Between 8 and 9 Between 4 and 5 Between 3 and 4 Undefined ................... Is'nt the root of any negative number undefined? not if it is  cube root(89) you are getting the cube root of 89 and then multiplying that by () that's my understanding



Math Expert
Joined: 02 Sep 2009
Posts: 44586

Re: cube root of (89) [#permalink]
Show Tags
03 Nov 2009, 18:46
2
This post received KUDOS
Expert's post
13
This post was BOOKMARKED
tejal777 wrote: The value of cube root of (89) is..? Between 9 and 10 Between 8 and 9 Between 4 and 5 Between 3 and 4 Undefined ................... Is'nt the root of any negative number undefined? Even roots from negative number is undefined on the GMAT (as GMAT is dealing only with Real Numbers): \(\sqrt[{even}]{negative}=undefined\), for example \(\sqrt{25}=undefined\). Odd roots will have the same sign as the base of the root. For example, \(\sqrt[3]{125} =5\) and \(\sqrt[3]{64} =4\). The above question is quite tricky: \(\sqrt[3]{89}\) is more than 5 (as \(5^3=125\)) but less than 4 (as \(4^3=64\)) > \(5<x<4\), (actually it's \(\approx{4.5}\)). So the the range would be between 5 and 4. The only answer choice to cover this range is A (9, 10). Answer: A.
_________________
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



VP
Joined: 05 Mar 2008
Posts: 1428

Re: cube root of (89) [#permalink]
Show Tags
03 Nov 2009, 18:47
Bunuel wrote: tejal777 wrote: The value of cube root of (89) is..? Between 9 and 10 Between 8 and 9 Between 4 and 5 Between 3 and 4 Undefined ................... Is'nt the root of any negative number undefined? The even root from negative power is undefined, for GMAT. For example: (negative number)^{1/2k} is undefined, (8)^1/2 or (3.5)^1/8 or (1)^1/22. But the odd root can be found. (2)*(2)*(2)=8 so (8)^1/3=2 or (4)*(4)*(4)=64 so (64)^1/3=4. The question you posted is quite tricky: (89)^1/3 is more than 5 (5^3=125) but less than 4 (4^3=64) > 5<x<4, (actually it's ~4.5). So the the range would be between 5 and 4. The only answer choice to cover this range is A (9, 10). Answer: A. forgot to answer the question...just curious if you typed the answers correctly...



Math Expert
Joined: 02 Sep 2009
Posts: 44586

Re: cube root of (89) [#permalink]
Show Tags
03 Nov 2009, 18:51



VP
Joined: 05 Mar 2008
Posts: 1428

Re: cube root of (89) [#permalink]
Show Tags
03 Nov 2009, 18:58
Bunuel wrote: lagomez wrote: forgot to answer the question...just curious if you typed the answers correctly... What you mean? What part are you referring to? sorry, meant the message for the original poster not you I see many questions like this on gmat review and always see the same signs for the answers, i.e., 9 to 10 not 9 to 10 my bad



Senior Manager
Joined: 18 Aug 2009
Posts: 390
Schools: UT at Austin, Indiana State University, UC at Berkeley
WE 1: 5.5
WE 2: 5.5
WE 3: 6.0

Re: cube root of (89) [#permalink]
Show Tags
03 Nov 2009, 22:13
Yeah, quite tricky question, if not bunuel, would hardly understoon it. Thanks.
_________________
Never give up,,,



Intern
Affiliations: CA  India
Joined: 27 Oct 2009
Posts: 44
Location: India
Schools: ISB  Hyderabad, NSU  Singapore

Re: cube root of (89) [#permalink]
Show Tags
03 Nov 2009, 22:22
i thought this was pretty simple by taking the answer options. E was out of question as the Bunual rightly mentioned.
only by looking at the lower limits of the ranges, we can discard option C and D.
Option B was a short ranged between 8 to 9 and the squares of these numbers are near 89. cube must be very high. without actually solving it, we can ignore it. Remaining option has to be the right one i.e. A.



Manager
Affiliations: SigEp
Joined: 12 Jun 2010
Posts: 67

Simple Cube Root [#permalink]
Show Tags
Updated on: 22 Aug 2010, 15:15
\(\sqrt[3]{89}\) is:
A) Between 9 and 10 B) Between 8 and 9 C) Between 4 and 5 D) Between 3 and 4 E) Undefined
My guess (D) was incorrect because I guess I did \(\sqrt[4]{81}= 3\) and \(\sqrt[3]{64}= 4\)
Originally posted by jcurry on 22 Aug 2010, 14:31.
Last edited by jcurry on 22 Aug 2010, 15:15, edited 1 time in total.



Math Expert
Joined: 02 Sep 2009
Posts: 44586

Re: Simple Cube Root [#permalink]
Show Tags
22 Aug 2010, 14:38



Manager
Affiliations: SigEp
Joined: 12 Jun 2010
Posts: 67

Re: cube root of (89) [#permalink]
Show Tags
22 Aug 2010, 15:03
Thanks I searched google and the forum but the math notation made it difficult to find.



Manager
Joined: 27 May 2010
Posts: 189

Re: cube root of (89) [#permalink]
Show Tags
22 Aug 2010, 20:31
Wow pretty similar questions. BTW will they ask such questions (like the first question where the answer choice is not very clear) on the GMAT?



Manager
Joined: 23 Apr 2010
Posts: 117
Location: Tx
Schools: NYU,UCLA,BOOTH,STANFORD

Re: cube root of (89) [#permalink]
Show Tags
06 Sep 2010, 08:23
Bunuel wrote: tejal777 wrote: The value of cube root of (89) is..? Between 9 and 10 Between 8 and 9 Between 4 and 5 Between 3 and 4 Undefined ................... Is'nt the root of any negative number undefined? Even roots from negative number is undefined on the GMAT (as GMAT is dealing only with Real Numbers): \(\sqrt[{even}]{negative}=undefined\), for example \(\sqrt{25}=undefined\). Odd roots will have the same sign as the base of the root. For example, \(\sqrt[3]{125} =5\) and \(\sqrt[3]{64} =4\). The above question is quite tricky: \(\sqrt[3]{89}\) is more than 5 (as \(5^3=125\)) but less than 4 (as \(4^3=64\)) > \(5<x<4\), (actually it's \(\approx{4.5}\)). So the the range would be between 5 and 4. The only answer choice to cover this range is A (9, 10). Answer: A. Hey bunuel i did this quesiton wrong cuz remember your words that \(\sqrt{25}=undefined\). cube root means that it has to be a negative number after you took out. Then it should be something \sqrt{negative X} therefore should be undefined? where am i missing?
_________________
This is not finished here...Watch me.....



Math Expert
Joined: 02 Sep 2009
Posts: 44586

Re: cube root of (89) [#permalink]
Show Tags
06 Sep 2010, 08:35
fatihaysu wrote: Bunuel wrote: tejal777 wrote: The value of cube root of (89) is..? Between 9 and 10 Between 8 and 9 Between 4 and 5 Between 3 and 4 Undefined ................... Is'nt the root of any negative number undefined? Even roots from negative number is undefined on the GMAT (as GMAT is dealing only with Real Numbers): \(\sqrt[{even}]{negative}=undefined\), for example \(\sqrt{25}=undefined\). Odd roots will have the same sign as the base of the root. For example, \(\sqrt[3]{125} =5\) and \(\sqrt[3]{64} =4\). The above question is quite tricky: \(\sqrt[3]{89}\) is more than 5 (as \(5^3=125\)) but less than 4 (as \(4^3=64\)) > \(5<x<4\), (actually it's \(\approx{4.5}\)). So the the range would be between 5 and 4. The only answer choice to cover this range is A (9, 10). Answer: A. Hey bunuel i did this quesiton wrong cuz remember your words that \(\sqrt{25}=undefined\). cube root means that it has to be a negative number after you took out. Then it should be something \sqrt{negative X} therefore should be undefined? where am i missing? Not sure that understand your question. But again: Even roots from negative number is undefined on the GMAT (as GMAT is dealing only with Real Numbers): \(\sqrt[{even}]{negative}=undefined\), for example \(\sqrt{25}=undefined\). Odd roots will have the same sign as the base of the root. For example, \(\sqrt[3]{125} =5\) and \(\sqrt[3]{64} =4\). Or: \(\sqrt[{even}]{positive}=positive\): \(\sqrt{25}=5\). Even roots have only a nonnegative value on the GMAT. \(\sqrt[{even}]{negative}=undefined\): \(\sqrt{25}=undefined\). Even roots from negative number is undefined on the GMAT (as GMAT is dealing only with Real Numbers). \(\sqrt[{odd}]{positive}=positive\) and \(\sqrt[{odd}]{negative}=negative\): \(\sqrt[3]{125} =5\) and \(\sqrt[3]{64} =4\). Odd roots will have the same sign as the base of the root.
_________________
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



Manager
Joined: 20 Apr 2010
Posts: 188
Schools: ISB, HEC, Said

Re: cube root of (89) [#permalink]
Show Tags
21 Sep 2010, 04:20
Hi Bunuel,
Is there any specific reason why GMAT want to confuse us with the Range that we calculate and actual range provided in the answer?



Math Expert
Joined: 02 Sep 2009
Posts: 44586

Re: cube root of (89) [#permalink]
Show Tags
21 Sep 2010, 04:46



Senior Manager
Joined: 29 Jan 2011
Posts: 319

Re: Simple Cube Root [#permalink]
Show Tags
06 Nov 2011, 13:44
jcurry wrote: \(\sqrt[3]{89}\) is:
A) Between 9 and 10 B) Between 8 and 9 C) Between 4 and 5 D) Between 3 and 4 E) Undefined
My guess (D) was incorrect because I guess I did \(\sqrt[4]{81}= 3\) and \(\sqrt[3]{64}= 4\) Are these 2 different questions ? Bunnels post says merging similar topics and they have different OA's ...I am not sure what the difference is ? The value of cube root of (89) is..? Between 9 and 10 Between 8 and 9 Between 4 and 5 Between 3 and 4 Undefined AND
\(\sqrt[3]{89}\) is: A) Between 9 and 10 B) Between 8 and 9 C) Between 4 and 5 D) Between 3 and 4 E) Undefined



Veritas Prep GMAT Instructor
Joined: 16 Oct 2010
Posts: 8026
Location: Pune, India

Re: Simple Cube Root [#permalink]
Show Tags
06 Nov 2011, 23:47
siddhans wrote: jcurry wrote: \(\sqrt[3]{89}\) is:
A) Between 9 and 10 B) Between 8 and 9 C) Between 4 and 5 D) Between 3 and 4 E) Undefined
My guess (D) was incorrect because I guess I did \(\sqrt[4]{81}= 3\) and \(\sqrt[3]{64}= 4\) Are these 2 different questions ? Bunnels post says merging similar topics and they have different OA's ...I am not sure what the difference is ? The value of cube root of (89) is..? Between 9 and 10 Between 8 and 9 Between 4 and 5 Between 3 and 4 Undefined AND
\(\sqrt[3]{89}\) is: A) Between 9 and 10 B) Between 8 and 9 C) Between 4 and 5 D) Between 3 and 4 E) Undefined The questions are the same but as Bunuel mentioned while merging, the answer options are different "Between 4 and 5" and "Between 4 and 5" The answer lies between 4 and 5 but not between 4 and 5 so the range which covers '4 to 5' is '9 to 10' in the first question.
_________________
Karishma Veritas Prep  GMAT Instructor My Blog
Get started with Veritas Prep GMAT On Demand for $199
Veritas Prep Reviews



Math Expert
Joined: 02 Sep 2009
Posts: 44586

Re: The value of cube root of (89) is: [#permalink]
Show Tags
05 Jun 2013, 04:27



Manager
Joined: 28 Feb 2012
Posts: 114
Concentration: Strategy, International Business
GPA: 3.9
WE: Marketing (Other)

Re: The value of cube root of (89) is: [#permalink]
Show Tags
06 Jun 2013, 06:58
tejal777 wrote: The value of cube root of (89) is:
A. Between 9 and 10 B. Between 8 and 9 C. Between 4 and 5 D. Between 3 and 4 E. Undefined Very tricky question. Questions seeks to find out for a range of numbers that include a number after multiplying it by itself gives 89. First thing we know is that it is a negative number. We can easily check few numbers, take 3*3*3=27 too low, 4*4*4=64 still low, 5*5*5=125 too big. So basically it should be a number between 4 and 5. Do we have such range? Trick here is that it is tmpting automatically go to choice C. But this is wrong choice because it does not cover the range required. The only range that includes number between 4 and 5 is A. Although it is very broad and covers many other values, but we have never been restricted. So the choice the A is the best!
_________________
If you found my post useful and/or interesting  you are welcome to give kudos!




Re: The value of cube root of (89) is:
[#permalink]
06 Jun 2013, 06:58



Go to page
1 2
Next
[ 31 posts ]



