December 10, 2018 December 10, 2018 10:00 PM PST 11:00 PM PST Practice the one most important Quant section  Integer properties, and rapidly improve your skills. December 11, 2018 December 11, 2018 09:00 PM EST 10:00 PM EST Strategies and techniques for approaching featured GMAT topics. December 11 at 9 PM EST.
Author 
Message 
TAGS:

Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 51072

If x is a positive integer, is x^(1/2) greater than 20?
[#permalink]
Show Tags
01 Nov 2015, 08:24
Question Stats:
81% (01:30) correct 19% (01:34) wrong based on 112 sessions
HideShow timer Statistics



Intern
Joined: 30 Aug 2015
Posts: 31
Concentration: Marketing, Finance
WE: Brand Management (Manufacturing)

Re: If x is a positive integer, is x^(1/2) greater than 20?
[#permalink]
Show Tags
01 Nov 2015, 10:05
Bunuel wrote: If x is a positive integer, is \(\sqrt{x}\) greater than 20?
(1) x is divisible by 30 (2) x is divisible by 50
Kudos for a correct solution. to be divisible by 30 . x can be 30 ,60 ,90 or we can say it can be multiple of 30 to be greater than x^(1/2) greater than 20 it can be or not be so ns point b. to be divisible by50 . x can be 50 ,100 or 150 we can say it can be multiple of 50 so not suffi lcm of 50 and 30 is 150 it can be 150 ,300,450 ,600 150^ is close to 13 600^ is greater than 20 .. so not suff Answer E
_________________
Please award kudos if you like my explanation. Thanks



Moderator
Joined: 21 Jun 2014
Posts: 1091
Location: India
Concentration: General Management, Technology
GPA: 2.49
WE: Information Technology (Computer Software)

Re: If x is a positive integer, is x^(1/2) greater than 20?
[#permalink]
Show Tags
01 Nov 2015, 11:30
x is a positive integer, is x√ greater than 20? It is given that x is positive. we can take the square on both side and hence the question is "is x > 400?" 1) x is divisible by 30  there are many numbers less than and greater than 400 are divisible by 30. So x can be less or greater than 400. 2) x is divisible by 50  there are many numbers less than and greater than 400 are divisible by 50. So x can be less or greater than 400. lets combine both the equations 1 & 2 to find out if the answer is C or E? X is such a number which is divisible by both 30 & 50. 150 is divisible by both 30 & 50. => X<400 600 is divisible by both 30 & 50, => X>400. So x can be less or greater than 400. Hence the answer is "E".
_________________
 Target  720740 Project PS Butler  https://gmatclub.com/forum/projectpsbutlerpracticeeveryday280904.html http://gmatclub.com/forum/informationonnewgmatesrreportbeta221111.html http://gmatclub.com/forum/listofoneyearfulltimembaprograms222103.html



Board of Directors
Joined: 17 Jul 2014
Posts: 2621
Location: United States (IL)
Concentration: Finance, Economics
GPA: 3.92
WE: General Management (Transportation)

Re: If x is a positive integer, is x^(1/2) greater than 20?
[#permalink]
Show Tags
01 Nov 2015, 11:35
x can't be 0 1  divisible by 30, x can be 30  in this case, sqrt 30 is not greater than 20, if x = 900 = yes, is greater. NS 2  divisible by 50, x can be 50 > in this case, sqrt 50 is 5 sqrt 2  not greater than 20. if x = 2500  yes, is greater. NS 1+2 > x can be 150, sqrt of 150 can be 5 sqrt 6 > not greater than 20. x can be 1500  and sqrt of 1500 is greater than 20. both are insufficient. E.



Intern
Joined: 30 Oct 2010
Posts: 49

Re: If x is a positive integer, is x^(1/2) greater than 20?
[#permalink]
Show Tags
Updated on: 01 Nov 2015, 13:31
Sqrt(X)>20 Squaring on both sides X>400
i)factors of 30=2x3x5 30,300,420 are also divisible by 30 So we dont have single value.So not sufficient
ii)factors of 50=2x5x5 50,240,500 are also divisible by 50 and So we dont have single value.So not sufficient
Combining i) & ii)
common factors = 2x3x5x5 =150 150,450 is also divisible by 150.we dont have single value.So not sufficient.
therefore the answer is E
Originally posted by iikarthik on 01 Nov 2015, 13:20.
Last edited by iikarthik on 01 Nov 2015, 13:31, edited 3 times in total.



Board of Directors
Joined: 17 Jul 2014
Posts: 2621
Location: United States (IL)
Concentration: Finance, Economics
GPA: 3.92
WE: General Management (Transportation)

Re: If x is a positive integer, is x^(1/2) greater than 20?
[#permalink]
Show Tags
01 Nov 2015, 13:22
iikarthik wrote: Sqrt(X)>20 Squaring on both sides X>400
i)factors of 30=2x3x5 30 is also divisible by 30 and <400.So not sufficient
ii)factors of 50=2x5x5 50 is also divisible by 30 and <400.So not sufficient
Combining i) & ii)
common factors = 2x3x5x5 =150 150 is still <400.So not sufficient.
therefore the answer is E mate, there are some serious flaws in your way of thinking. first of all, when analyzing statement 2, do not, do not, do not use any information from statement 1. second, as you have pointed out, 150 is <400. This is a Yes/No DS type of question. IF you can clearly say Yes or No, then the information is sufficient. From your msg, you say that 150 is less than 400, that's why it is not sufficient. That's not true. third, 50 is not divisible by 30, since the prime factorization is different. 30 has 3 distinct factors 2, 3, and 5, while 50 has only 2 distinct factors: 2 and 5.



Intern
Joined: 30 Oct 2010
Posts: 49

Re: If x is a positive integer, is x^(1/2) greater than 20?
[#permalink]
Show Tags
01 Nov 2015, 13:30
mvictor wrote: iikarthik wrote: Sqrt(X)>20 Squaring on both sides X>400
i)factors of 30=2x3x5 30 is also divisible by 30 and <400.So not sufficient
ii)factors of 50=2x5x5 50 is also divisible by 30 and <400.So not sufficient
Combining i) & ii)
common factors = 2x3x5x5 =150 150 is still <400.So not sufficient.
therefore the answer is E mate, there are some serious flaws in your way of thinking. first of all, when analyzing statement 2, do not, do not, do not use any information from statement 1. second, as you have pointed out, 150 is <400. This is a Yes/No DS type of question. IF you can clearly say Yes or No, then the information is sufficient. From your msg, you say that 150 is less than 400, that's why it is not sufficient. That's not true. third, 50 is not divisible by 30, since the prime factorization is different. 30 has 3 distinct factors 2, 3, and 5, while 50 has only 2 distinct factors: 2 and 5. Thanks Mvictor for pointing out the typo and logical flaws.Hope it si correct now. I have edited my post



Intern
Joined: 05 Apr 2015
Posts: 10

Re: If x is a positive integer, is x^(1/2) greater than 20?
[#permalink]
Show Tags
02 Nov 2015, 08:01
orig condition is x>400?
1. x divisibly by 30, i.e. x=30,600etc.. not suff 2. x divisible by 50 i.e. x =50,500 etc. not suff combining both, x= 150, 1500 etc.. so not suff. ANS :E



Math Revolution GMAT Instructor
Joined: 16 Aug 2015
Posts: 6616
GPA: 3.82

Re: If x is a positive integer, is x^(1/2) greater than 20?
[#permalink]
Show Tags
04 Nov 2015, 10:13
Forget conventional ways of solving math questions. In DS, Variable approach is the easiest and quickest way to find the answer without actually solving the problem. Remember equal number of variables and independent equations ensures a solution. If x is a positive integer, is x √ greater than 20? (1) x is divisible by 30 (2) x is divisible by 50 If we modify the original condition by squaring both sides, we get x>20^2 or x>400. There is one variable (x) and 2 equations are given from the conditions, so there is high chance (D) will be our answer. From condition 1, the answer is 'no' for x=30 but 'yes' for 1500. This is insufficient. For condition 2, the answer is 'no' for x=50 but 'yes' for 1500. This is insufficient. Looking at the conditions together, the answer is 'no' for x=150 but 'yes' for 1500. So the answer becomes (E). For cases where we need 1 more equation, such as original conditions with “1 variable”, or “2 variables and 1 equation”, or “3 variables and 2 equations”, we have 1 equation each in both 1) and 2). Therefore, there is 59 % chance that D is the answer, while A or B has 38% chance and C or E has 3% chance. Since D is most likely to be the answer using 1) and 2) separately according to DS definition. Obviously there may be cases where the answer is A, B, C or E.
_________________
MathRevolution: Finish GMAT Quant Section with 10 minutes to spare The oneandonly World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy. "Only $99 for 3 month Online Course" "Free Resources30 day online access & Diagnostic Test" "Unlimited Access to over 120 free video lessons  try it yourself"



Intern
Joined: 12 Jul 2017
Posts: 18

Re: If x is a positive integer, is x^(1/2) greater than 20?
[#permalink]
Show Tags
14 Jul 2017, 09:40
lcm of 50 and 30 is 150 it can be 150 ,300 ,450 ,600 150^ is close to 13 600^ is greater than 20 .. so not sufficient Answer is E



NonHuman User
Joined: 09 Sep 2013
Posts: 9101

Re: If x is a positive integer, is x^(1/2) greater than 20?
[#permalink]
Show Tags
19 Jul 2018, 06:20
Hello from the GMAT Club BumpBot! Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up  doing my job. I think you may find it valuable (esp those replies with Kudos). Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________
GMAT Books  GMAT Club Tests  Best Prices on GMAT Courses  GMAT Mobile App  Math Resources  Verbal Resources




Re: If x is a positive integer, is x^(1/2) greater than 20? &nbs
[#permalink]
19 Jul 2018, 06:20






