January 26, 2019 January 26, 2019 07:00 AM PST 09:00 AM PST Attend this webinar to learn how to leverage Meaning and Logic to solve the most challenging Sentence Correction Questions. January 27, 2019 January 27, 2019 07:00 AM PST 09:00 AM PST Attend this webinar to learn a structured approach to solve 700+ Number Properties question in less than 2 minutes.
Author 
Message 
TAGS:

Hide Tags

Manager
Joined: 10 Nov 2010
Posts: 132

If every member of set X {14, 12, 17, 28, 41, Z} is
[#permalink]
Show Tags
26 Mar 2011, 23:07
Question Stats:
66% (02:01) correct 34% (02:03) wrong based on 474 sessions
HideShow timer Statistics
If every member of set X {14, 12, 17, 28, 41, Z} is multiplied by number N, by what percent will the mean M of the set increase? (1) Z = 60 (2) N = Z / M
Official Answer and Stats are available only to registered users. Register/ Login.




Retired Moderator
Joined: 20 Dec 2010
Posts: 1810

Re: Mean after multiplying
[#permalink]
Show Tags
27 Mar 2011, 00:00
vjsharma25 wrote: If every member of set X {14, 12, 17, 28, 41, Z} is multiplied by number N, by what percent will the mean M of the set increase? (A) Z = 60 (B) N = Z / M I don't have answer for this.But I think answer should be . X {14, 12, 17, 28, 41, Z} If all the numbers are multiplied by a constant, the mean will also increase by that constant. 1. Z=60 We get a mean of 20 here initially. If the set is multiplied by 10, the new mean becomes 200, increasing the mean by 900% If the set is multiplied by 2, the new mean becomes 40, increasing the mean by 100% We must find an exact value of multiplier or mean to find the percent increase in mean. Not Sufficient. 2. N = Z / M (14, 12, 17, 28, 41 + Z)/6 = M 60+Z=6M N = Z / M; Z=NM 60+NM=6M. Not Sufficient to find an exact mean or multiplier. Not Sufficient. Combining both; 60+NM=6M NM=Z=60 60+60=6M M = 120/6= 20 And N = Z/M = 60/20=3 We know the multiplier. Sufficient. Ans: "C" P.S.: The new mean will increase by 20% because the multiplier is 3. We wouldn't need "Z" if we knew the multiplier, however in this case; we needed Z to find the multiplier.
_________________
~fluke
GMAT Club Premium Membership  big benefits and savings




Manager
Joined: 10 Nov 2010
Posts: 132

Re: Mean after multiplying
[#permalink]
Show Tags
26 Mar 2011, 23:43
gmat1220 wrote: I think this is loner. It is A. But after multiplying every number by N,N will come into picture for new mean. And if you don't know N u can't calculate the % increase. Taking statement A into effect Old Mean = 120/6 New mean = 120N/6 You don't have N!!



Director
Status: Impossible is not a fact. It's an opinion. It's a dare. Impossible is nothing.
Affiliations: University of Chicago Booth School of Business
Joined: 03 Feb 2011
Posts: 728

Re: Mean after multiplying
[#permalink]
Show Tags
27 Mar 2011, 00:21
Guys, Btw do you know where is Bunuel is these days? He is seldom online now.



Retired Moderator
Joined: 20 Dec 2010
Posts: 1810

Re: Mean after multiplying
[#permalink]
Show Tags
27 Mar 2011, 00:32
gmat1220 wrote: Guys, Btw do you know where is Bunuel is these days? He is seldom online now. You know what, "I was wondering about the same". Please come back soon Legend, we are deprived of your elegant solutions/approach. Perhaps "bb" can tell us where he is these days and when will he be coming back.
_________________
~fluke
GMAT Club Premium Membership  big benefits and savings



Retired Moderator
Joined: 16 Nov 2010
Posts: 1419
Location: United States (IN)
Concentration: Strategy, Technology

Re: Mean after multiplying
[#permalink]
Show Tags
27 Mar 2011, 02:48
Mean , M = (14 + 12 + 17 + 28 + 41 + Z)/6 => M = (26 + 86 + Z)/6 => M = (60 + Z)/6 M1 = (60N + ZN)/6 So (M1  M)/M = ? {60(N1) + Z(N1)}/(60 + Z) = ? From (1) Z = 60, but (N1) does not cancel out From (2) N = Z/M, Z/N = (60 + Z)/6 => N = 6Z/(60 + Z) not sufficient From (1) and (2) M= 60/N (60 + 60)/6 = 60/N => N = 3 So the values can be obtained further Answer  C
_________________
Formula of Life > Achievement/Potential = k * Happiness (where k is a constant)
GMAT Club Premium Membership  big benefits and savings



Director
Joined: 01 Feb 2011
Posts: 658

Re: Mean after multiplying
[#permalink]
Show Tags
02 Apr 2011, 18:10
M = (60+z)/6
New Mean (lets say M1) = N(60+z)/6
% increase = ((M1M)/M)*100 = (N1)*100
1. Z =60
=> M = 20
no info on N. So not enough to calculate % increase. Not sufficient.
2. N = Z/M
not enough to calculate % increase ( because we dont know Z or M here)
together Z=0, M = 20 , N = Z/M = 3 , enough to calculate % increase.
Answer C.



Intern
Joined: 17 Jun 2013
Posts: 4

Re: If every member of set X {14, 12, 17, 28, 41, Z} is
[#permalink]
Show Tags
26 Jun 2013, 06:34
ANSWER : A
If every member of set X {14, 12, 17, 28, 41, Z} is multiplied by number N, by what percent will the mean M of the set increase? (A) Z = 60 (B) N = Z / M
ANS (A) : The set totals to 120 provided 60 (Z) is added to it and therefore the mean is 20. Now let's take an assumption for "N" i.e 2 and multiply it. So the the mean now is 40 which is 200 % of 20. Therefore sufficient. Further N can be assumed as odd no. and the % can be calculated therefore sufficient.
ANS (B) : N, here can be assumed as a number but what is Z (can be any no. again) and the mean depends on Z. Therefore insufficient. AD/BCE split



Math Expert
Joined: 02 Sep 2009
Posts: 52438

Re: If every member of set X {14, 12, 17, 28, 41, Z} is
[#permalink]
Show Tags
26 Jun 2013, 07:01
dasikasuneel wrote: ANSWER : A
If every member of set X {14, 12, 17, 28, 41, Z} is multiplied by number N, by what percent will the mean M of the set increase? (A) Z = 60 (B) N = Z / M
ANS (A) : The set totals to 120 provided 60 (Z) is added to it and therefore the mean is 20. Now let's take an assumption for "N" i.e 2 and multiply it. So the the mean now is 40 which is 200 % of 20. Therefore sufficient. Further N can be assumed as odd no. and the % can be calculated therefore sufficient.
ANS (B) : N, here can be assumed as a number but what is Z (can be any no. again) and the mean depends on Z. Therefore insufficient. AD/BCE split Please note that the OA for this question is C, not A. When a DS question asks about the value of some variable, then the statement is sufficient ONLY if you can get the single numerical value of this variable.Different N's will give you different numerical increase for (1). 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: 16 Nov 2013
Posts: 28
Location: United States
Concentration: Entrepreneurship, General Management
GPA: 3.49

Re: Mean after multiplying
[#permalink]
Show Tags
19 Nov 2013, 08:33
fluke wrote: vjsharma25 wrote: If every member of set X {14, 12, 17, 28, 41, Z} is multiplied by number N, by what percent will the mean M of the set increase? (A) Z = 60 (B) N = Z / M I don't have answer for this.But I think answer should be . X {14, 12, 17, 28, 41, Z} If all the numbers are multiplied by a constant, the mean will also increase by that constant. 1. Z=60 We get a mean of 20 here initially. If the set is multiplied by 10, the new mean becomes 200, increasing the mean by 900% If the set is multiplied by 2, the new mean becomes 40, increasing the mean by 100% We must find an exact value of multiplier or mean to find the percent increase in mean. Not Sufficient. 2. N = Z / M (14, 12, 17, 28, 41 + Z)/6 = M 60+Z=6M N = Z / M; Z=NM 60+NM=6M. Not Sufficient to find an exact mean or multiplier. Not Sufficient. Combining both; 60+NM=6M NM=Z=60 60+60=6M M = 120/6= 20 And N = Z/M = 60/20=3 We know the multiplier. Sufficient. Ans: "C" P.S.: The new mean will increase by 20% because the multiplier is 3. We wouldn't need "Z" if we knew the multiplier, however in this case; we needed Z to find the multiplier.I don't understand how you know the mean will increase by 20% by knowing that the multiplier is 3 (and not needing to know "Z")



Intern
Status: Miles to go....before i sleep
Joined: 26 May 2013
Posts: 14
Location: India
Concentration: Finance, Marketing

Re: If every member of set X {14, 12, 17, 28, 41, Z} is
[#permalink]
Show Tags
07 Dec 2013, 05:51
If every member of set X {14, 12, 17, 28, 41, Z} is multiplied by number N, by what percent will the mean M of the set increase?
(1) Z = 60 (2) N = Z / M
Solution: If we increase/decrease each term in a set by the same percent( multiply all the terms by a constant), mean will increase/decrease by same percent. So, to know the percent increase in the mean we have to find 'N'
(1) By knowing the value of Z, we can find the value M, but we do not know the value of 'N' : Insufficient (2) Since Z is unknown, we cannot find 'N': Insufficient
(1)+(2) By first we can find the values of Z and M, which are 60 and 20 respectively, and by (2) we can find 'N', which is 3 Sufficient
Answer: C



Intern
Joined: 08 Jun 2016
Posts: 10

Re: If every member of set X {14, 12, 17, 28, 41, Z} is
[#permalink]
Show Tags
10 Aug 2016, 13:26
Since, Z is not defined and N is not given in the question .. We cannot get the answer if anyone of these two miss..
Option 1, can only find Z not N. Hence insufficient.
Option 2, cannot find any of them..
However, combining both can get the value of Z and N
Hence, option C is correct
Sent from my AO5510 using Tapatalk



Current Student
Joined: 08 Jun 2013
Posts: 33

Re: If every member of set X {14, 12, 17, 28, 41, Z} is
[#permalink]
Show Tags
18 Sep 2016, 04:21
A) Z=60 by knowing the value of z we can calculate mean of set but for percent increase in mean when multiplied by N, value of N is required. Not suff B) N= Z/M without value of Z, M can't be found out and without value of M and Z, N can't be found out Not Suff So, combining we have value of Z and further value of M and N, hence percentage increase can be calculated Answer is C.



Intern
Joined: 18 Aug 2017
Posts: 19

Re: If every member of set X {14, 12, 17, 28, 41, Z} is
[#permalink]
Show Tags
01 Oct 2018, 08:32
fluke wrote: vjsharma25 wrote: If every member of set X {14, 12, 17, 28, 41, Z} is multiplied by number N, by what percent will the mean M of the set increase? (A) Z = 60 (B) N = Z / M I don't have answer for this.But I think answer should be . X {14, 12, 17, 28, 41, Z} If all the numbers are multiplied by a constant, the mean will also increase by that constant. 1. Z=60 We get a mean of 20 here initially. If the set is multiplied by 10, the new mean becomes 200, increasing the mean by 900% If the set is multiplied by 2, the new mean becomes 40, increasing the mean by 100% We must find an exact value of multiplier or mean to find the percent increase in mean. Not Sufficient. 2. N = Z / M (14, 12, 17, 28, 41 + Z)/6 = M 60+Z=6M N = Z / M; Z=NM 60+NM=6M. Not Sufficient to find an exact mean or multiplier. Not Sufficient. Combining both; 60+NM=6M NM=Z=60 60+60=6M M = 120/6= 20 And N = Z/M = 60/20=3 We know the multiplier. Sufficient. Ans: "C" P.S.: The new mean will increase by 20% because the multiplier is 3. We wouldn't need "Z" if we knew the multiplier, however in this case; we needed Z to find the multiplier. What is the level of this question? Sent from my ONEPLUS A3003 using GMAT Club Forum mobile app
_________________
I believe myself




Re: If every member of set X {14, 12, 17, 28, 41, Z} is &nbs
[#permalink]
01 Oct 2018, 08:32






