Author 
Message 
TAGS:

Hide Tags

Retired Moderator
Joined: 17 Sep 2013
Posts: 362
Concentration: Strategy, General Management
WE: Analyst (Consulting)

The table above shows daily energy usage for an office building and th
[#permalink]
Show Tags
20 Dec 2014, 07:06
Question Stats:
50% (03:20) correct 50% (02:58) wrong based on 145 sessions
HideShow timer Statistics
Energy Usage Units  11, 10, 8, 7 Number of Days of the respective unit 4, 5, n, 3 The table above shows daily energy usage for an office building and the number of days that amount of energy was used. If the average (arithmetic mean) daily energy usage was greater than the median daily energy usage, what is the smallest possible value for n? (A) 2 (B) 3 (C) 4 (D) 5 (E) 6
Official Answer and Stats are available only to registered users. Register/ Login.
_________________
Appreciate the efforts...KUDOS for all Don't let an extra chromosome get you down..




EMPOWERgmat Instructor
Status: GMAT Assassin/CoFounder
Affiliations: EMPOWERgmat
Joined: 19 Dec 2014
Posts: 12407
Location: United States (CA)

Re: The table above shows daily energy usage for an office building and th
[#permalink]
Show Tags
20 Dec 2014, 19:13
Hi JusTLucK04, This question can be solved by TESTing THE ANSWERS. Before we get to that though, I'm going to recreate a real basic version of the "table" that you're describing: En Used  # of Days: 11 > 4 10 > 5 8 > N 7 > 3 We're told that the AVERAGE daily use > MEDIAN daily use. We're then asked for the SMALLEST possible value of N. The value of N will impact both the average and the median, but there is a pattern/shortcut worth noting: If N = 2, 3, 4, or 5, then the MEDIAN = 10 If N = 6, then the Median = 9 The average of the numbers will be: (115 + 8N)/(12 + N) So we're really just looking for the SMALLEST relative value of N that will give us an average that is greater than 10 (in 4 of the options) or 9 (in the fifth option). From here, we can either "brute force" the options to find the match or do some algebra to disprove the wrong answers. Since 4 of the answers have the same median (10), I'm going to focus on THAT group. For the average to be > the median, we'd have... (115 + 8N)/12 + N) > 10 115 + 8N > 10(12 + N) 115 + 8N > 120 + 10N 2N > 5 N < 5/2 This tells us that N would have to be a NEGATIVE number, which is not possible. This eliminates answers A through D (since they're all POSITIVE and they all have the same median of 10). Final Answer: Here's the proof that it's the correct answer: Since that answer would gives us a median of 9, we'd have... (115 + 8N)/(12 + N) > 9 115 + 8N > 9(12 + N) 115 + 8N > 108 + 9N 7 > N This is the only answer that gives us a range for N that includes the actual answer choice that generated the range. GMAT assassins aren't born, they're made, Rich
_________________
760+: Learn What GMAT Assassins Do to Score at the Highest Levels Contact Rich at: Rich.C@empowergmat.com
Rich Cohen
CoFounder & GMAT Assassin
Special Offer: Save $75 + GMAT Club Tests Free
Official GMAT Exam Packs + 70 Pt. Improvement Guarantee www.empowergmat.com/
***********************Select EMPOWERgmat Courses now include ALL 6 Official GMAC CATs!***********************




Director
Status: Everyone is a leader. Just stop listening to others.
Joined: 22 Mar 2013
Posts: 844
Location: India
GPA: 3.51
WE: Information Technology (Computer Software)

Re: The table above shows daily energy usage for an office building and th
[#permalink]
Show Tags
20 Dec 2014, 21:10
I think testing the values is one of the convenient ways. Initially I wasted time thinking on strategy, but later found hit and trial much promising. I got E, but spent approx 45 min on this.
_________________
Piyush K
 Our greatest weakness lies in giving up. The most certain way to succeed is to try just one more time. ― Thomas A. Edison Don't forget to press> Kudos My Articles: 1. WOULD: when to use?  2. All GMATPrep RCs (New) Tip: Before exam a week earlier don't forget to exhaust all gmatprep problems specially for "sentence correction".



EMPOWERgmat Instructor
Status: GMAT Assassin/CoFounder
Affiliations: EMPOWERgmat
Joined: 19 Dec 2014
Posts: 12407
Location: United States (CA)

Re: The table above shows daily energy usage for an office building and th
[#permalink]
Show Tags
21 Dec 2014, 19:50
Hi PiyushK, Most of the GMAT questions that you'll see on Test Day can be solved in a variety of ways, so beyond learning the "math approach" that the OG13/GMAT2015 usually emphasizes, it's important to practice the various tactical approaches too. Here, the question itself gives you a HUGE clue as to how to solve it...."what is the smallest possible value for N?" AND the answers are 5 numbers. Part of maximizing your performance on Test Day is in finding all the little clues that the GMAT writers leave for you...and then taking advantage of those clues. GMAT assassins aren't born, they're made, Rich
_________________
760+: Learn What GMAT Assassins Do to Score at the Highest Levels Contact Rich at: Rich.C@empowergmat.com
Rich Cohen
CoFounder & GMAT Assassin
Special Offer: Save $75 + GMAT Club Tests Free
Official GMAT Exam Packs + 70 Pt. Improvement Guarantee www.empowergmat.com/
***********************Select EMPOWERgmat Courses now include ALL 6 Official GMAC CATs!***********************



Manager
Joined: 22 Aug 2014
Posts: 173

Re: The table above shows daily energy usage for an office building and th
[#permalink]
Show Tags
29 Mar 2015, 05:09
Please help me to understand this. I got the below equation;
(115+8n/12+n)>9 here even 2(smallest value in answer choice) satisfies the equation
(115+16/14)>9 131>14*9 131>126
Then why 6 is the smallest value?



Math Expert
Joined: 02 Aug 2009
Posts: 6785

Re: The table above shows daily energy usage for an office building and th
[#permalink]
Show Tags
29 Mar 2015, 05:28
ssriva2 wrote: Please help me to understand this. I got the below equation;
(115+8n/12+n)>9 here even 2(smallest value in answer choice) satisfies the equation
(115+16/14)>9 131>14*9 131>126
Then why 6 is the smallest value? hi ssriva2, the median value would depend on the value of n and would not be 9 in every case... lets look at the table unitsdays 11  4 10  5 8  n 7  3... or to find median , we can write it as 11,11,11,11,10,10,10,10,10,8..n times,7,7,7.. so if n+3<4+5... median is 10.. n can take values of 2,3,4,5.... but when n+3=4+5.. median will be(8+10)/2=9.. now substitue in your eqn to find answer... eq 1 : (115 + 8N)/(12 + N) > 10, if n=2,3,4,5 eq 2: (115 + 8N)/(12 + N) > 9, if n=6.. only n=6 satisfies the eq.. hope it helped
_________________
1) Absolute modulus : http://gmatclub.com/forum/absolutemodulusabetterunderstanding210849.html#p1622372 2)Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html 3) effects of arithmetic operations : https://gmatclub.com/forum/effectsofarithmeticoperationsonfractions269413.html
GMAT online Tutor



Senior Manager
Joined: 29 Dec 2017
Posts: 378
Location: United States
Concentration: Marketing, Technology
GMAT 1: 630 Q44 V33 GMAT 2: 690 Q47 V37
GPA: 3.25
WE: Marketing (Telecommunications)

The table above shows daily energy usage for an office building and th
[#permalink]
Show Tags
15 Apr 2018, 14:47
chetan2u wrote: ssriva2 wrote: Please help me to understand this. I got the below equation;
(115+8n/12+n)>9 here even 2(smallest value in answer choice) satisfies the equation
(115+16/14)>9 131>14*9 131>126
Then why 6 is the smallest value? hi ssriva2, the median value would depend on the value of n and would not be 9 in every case... lets look at the table unitsdays 11  4 10  5 8  n 7  3... or to find median , we can write it as 11,11,11,11,10,10,10,10,10,8..n times,7,7,7.. so if n+3<4+5... median is 10.. n can take values of 2,3,4,5.... but when n+3=4+5.. median will be(8+10)/2=9.. now substitue in your eqn to find answer... eq 1 : (115 + 8N)/(12 + N) > 10, if n=2,3,4,5 eq 2: (115 + 8N)/(12 + N) > 9, if n=6.. only n=6 satisfies the eq.. hope it helped Hi, Can you explain how to find the median if have two related sets as in this case? And what if we had odd number of digits in the sets? Thanks




The table above shows daily energy usage for an office building and th &nbs
[#permalink]
15 Apr 2018, 14:47






