Mar 20 07:00 AM PDT  09:00 AM PDT Join a FREE 1day workshop and learn how to ace the GMAT while keeping your fulltime job. Limited for the first 99 registrants. Mar 19 08:00 AM PDT  09:00 AM PDT Beat the GMAT with a customized study plan based on your needs! Learn how to create your preparation timeline, what makes a good study plan and which tools you need to use to build the perfect plan. Register today! Mar 20 09:00 PM EDT  10:00 PM EDT Strategies and techniques for approaching featured GMAT topics. Wednesday, March 20th at 9 PM EDT Mar 23 07:00 AM PDT  09:00 AM PDT Christina scored 760 by having clear (ability) milestones and a trackable plan to achieve the same. Attend this webinar to learn how to build trackable milestones that leverage your strengths to help you get to your target GMAT score.
Author 
Message 
TAGS:

Hide Tags

Intern
Joined: 24 Jan 2014
Posts: 10

The cost per unit of electricity during a 4 year period is a
[#permalink]
Show Tags
Updated on: 08 Apr 2014, 01:31
Question Stats:
62% (02:30) correct 38% (02:16) wrong based on 245 sessions
HideShow timer Statistics
The cost per unit of electricity during a 4 year period is as follows: Year 1, $1 per unit; Year 2, $1.5 per unit; Year 3, $1.2 per unit; Year 4, $2 per unit. If a factory spent equal dollars on electricity each year, what was the average cost of a unit of electricity during the 4 year period? A. $1.333 B. $1.250 C. $1.425 D. $1.175 E. $1.500
Official Answer and Stats are available only to registered users. Register/ Login.
Originally posted by Safal on 07 Apr 2014, 22:18.
Last edited by Bunuel on 08 Apr 2014, 01:31, edited 4 times in total.
Edited the question




VP
Joined: 02 Jul 2012
Posts: 1161
Location: India
Concentration: Strategy
GPA: 3.8
WE: Engineering (Energy and Utilities)

Re: Try this out!
[#permalink]
Show Tags
07 Apr 2014, 22:23
Let money spent each year = $6 Units bought first year = 6 Units bought second year = 4 Units bought third year = 5 Units bought fourth year = 3 Total number of units = 18 Total money spent = 6*4 = 24 Average = 24/18 = 4/3 = 1.33 Answer is A
_________________
Did you find this post helpful?... Please let me know through the Kudos button.
Thanks To The Almighty  My GMAT Debrief
GMAT Reading Comprehension: 7 Most Common Passage Types




Manager
Joined: 08 Nov 2014
Posts: 81
Location: India
GPA: 3
WE: Engineering (Manufacturing)

Re: The cost per unit of electricity during a 4 year period is a
[#permalink]
Show Tags
13 Mar 2015, 11:51
[align=]It can be solved by weighted average formula, which is = ( x1*n1+x2*n2+x3*n3+......................)/(n1+n2+n3+...............)where, x1,x2,x3 are values assigned and, n1,n2,n3 are the frequency or no. of repetition of x1,x2,x3 respwctively. As problem states: x1*n1=x2*n2=x3*n3=x4*n4 LCM of (x i )1,1.5,1.2,and 2 is 6 Therefore n1=6, n2=4, n3=5and n4= 3 Calculating average using above formula Avg.= 4*6/(6+4+5+3) = 1.33[/align]
_________________
"Arise, Awake and Stop not till the goal is reached"



Board of Directors
Joined: 17 Jul 2014
Posts: 2562
Location: United States (IL)
Concentration: Finance, Economics
GPA: 3.92
WE: General Management (Transportation)

Re: The cost per unit of electricity during a 4 year period is a
[#permalink]
Show Tags
15 Feb 2016, 19:55
my approach was to pick a number that would be easy to divide by all the prices given. suppose company spent 12$ each year. 1st year  used 12 units 2nd year  8 units 3rd year  10 units 4th year  6 units total, we have 36 units. since 12$/year was spent, in all 4 years was spent 48$. now, avg price is total $/total # units = 48/36 = 4/3 or 1.33
A.



Veritas Prep GMAT Instructor
Joined: 16 Oct 2010
Posts: 8988
Location: Pune, India

Re: The cost per unit of electricity during a 4 year period is a
[#permalink]
Show Tags
15 Feb 2016, 22:01
Safal wrote: The cost per unit of electricity during a 4 year period is as follows:
Year 1, $1 per unit; Year 2, $1.5 per unit; Year 3, $1.2 per unit; Year 4, $2 per unit.
If a factory spent equal dollars on electricity each year, what was the average cost of a unit of electricity during the 4 year period?
A. $1.333 B. $1.250 C. $1.425 D. $1.175 E. $1.500 Here is another method for the more mathematically inclined. When we talk about equal amount of money spent, the average price is the harmonic mean of all the prices. \(1/1 + \frac{1}{1.5} + \frac{1}{1.2} + \frac{1}{2} = \frac{4}{H}\) \(\frac{6}{6} + \frac{4}{6} + \frac{5}{6} + \frac{3}{6} = \frac{4}{H}\) \(H = \frac{4}{3} = 1.333\) Answer (A)
_________________
Karishma Veritas Prep GMAT Instructor
Learn more about how Veritas Prep can help you achieve a great GMAT score by checking out their GMAT Prep Options >



Math Expert
Joined: 02 Aug 2009
Posts: 7415

Re: The cost per unit of electricity during a 4 year period is a
[#permalink]
Show Tags
16 Feb 2016, 00:56
Safal wrote: The cost per unit of electricity during a 4 year period is as follows:
Year 1, $1 per unit; Year 2, $1.5 per unit; Year 3, $1.2 per unit; Year 4, $2 per unit.
If a factory spent equal dollars on electricity each year, what was the average cost of a unit of electricity during the 4 year period?
A. $1.333 B. $1.250 C. $1.425 D. $1.175 E. $1.500 Hi all, you cannot apply AVERAGE straightway as the units are not the same for each year, example the expense at $1 is higher than at $2.. Also we cannot apply weighted average as we have four quantities and that too in not proper form..there can be two ways... arithmetic way choose a number, which is LCM of all four, say 6 here.. how much can you purchase Year 1, $1 per unit;  6/1=6 units Year 2, $1.5 per unit;  6/1.5=4 units Year 3, $1.2 per unit;  6/1.2=5 units Year 4, $2 per unit.  6/2=3 units... total units = 6+4+5+3=18 units.. cost incurred = 6*4=24.. avg cost= 24/18=1.333Weighted average lets test weighted average for two pairs separately.. also since overall expenditure is same each year, the units will be proportional to cost..1) $1 and $2.. the ratio of units is 2:1, so the weighted average will be 1+(21)* 1/(1+2)= 1.333 2) $1.5 and %1.2.. ratio of units = 1.5:1.2... so weighted average= 1.2 + 1.5/(1.2+1.5)= 1.2+(1.51.2)*1.5/2.7= 1.2 + 3*1.5/27= 1.2+ 1/6= 1.2+ 0.1333= 1.333..
now we have two quantities with the same average rate= 1.333, so their combined averge rate will also be 1.333NOTE: the answer will be lesser than the average of the cost, as while doing so we take the qty at each price to be same, whereas the quantities are higher for lower values.. so average< (1+1.5+1.2+2)/4= 1.425.. you can straight way eliminate C and E..
_________________
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 4) Base while finding % increase and % decrease : https://gmatclub.com/forum/percentageincreasedecreasewhatshouldbethedenominator287528.html
GMAT Expert



Intern
Joined: 11 Oct 2012
Posts: 33

Re: The cost per unit of electricity during a 4 year period is a
[#permalink]
Show Tags
16 Feb 2016, 08:08
VeritasPrepKarishma wrote: Safal wrote: The cost per unit of electricity during a 4 year period is as follows:
Year 1, $1 per unit; Year 2, $1.5 per unit; Year 3, $1.2 per unit; Year 4, $2 per unit.
If a factory spent equal dollars on electricity each year, what was the average cost of a unit of electricity during the 4 year period?
A. $1.333 B. $1.250 C. $1.425 D. $1.175 E. $1.500 Here is another method for the more mathematically inclined. When we talk about equal amount of money spent, the average price is the harmonic mean of all the prices. \(1/1 + \frac{1}{1.5} + \frac{1}{1.2} + \frac{1}{2} = \frac{4}{H}\) \(\frac{6}{6} + \frac{4}{6} + \frac{5}{6} + \frac{3}{6} = \frac{4}{H}\) \(H = \frac{4}{3} = 1.333\) Answer (A) Hi Karishma, Is there any mathematical principal for this ?



Board of Directors
Status: QA & VA Forum Moderator
Joined: 11 Jun 2011
Posts: 4402
Location: India
GPA: 3.5
WE: Business Development (Commercial Banking)

Re: The cost per unit of electricity during a 4 year period is a
[#permalink]
Show Tags
16 Feb 2016, 08:54
Safal wrote: The cost per unit of electricity during a 4 year period is as follows:
Year 1, $1 per unit; Year 2, $1.5 per unit; Year 3, $1.2 per unit; Year 4, $2 per unit.
If a factory spent equal dollars on electricity each year, what was the average cost of a unit of electricity during the 4 year period?
A. $1.333 B. $1.250 C. $1.425 D. $1.175 E. $1.500 Since equal dollars is spent on electricity each year we take the LCM of 1, 1.2, 1.5 & 2 ; ie  6 So, We get the factory spent $6 dollar each year ( Year 1  Year 4 ), so during the 4 years they spent $ 24 Now, calculate the unit of electricity consumed. Unit of electricity consumed = Total Cost /Cost per unit of electricity Now, calculate the consumption Year wise Year 1 = 6/1 =>6 units Year 2 = 6/1.5 => 4 units Year 3 = 6/1.2 => 5 units Year 4 = 6/2 => 3 units Total consumption during the four years is ( 6+4+5+3) 18 units. We are asked to find  Quote: the average cost of a unit of electricity during the 4 year period Average cost of a unit of electricity = Total cost of electricity during the 4 years / Total Consumption during the 4 years. Average cost of a unit of electricity = 24 /18 =>1.33 Hence answer is (A)
_________________
Thanks and Regards
Abhishek....
PLEASE FOLLOW THE RULES FOR POSTING IN QA AND VA FORUM AND USE SEARCH FUNCTION BEFORE POSTING NEW QUESTIONS
How to use Search Function in GMAT Club  Rules for Posting in QA forum  Writing Mathematical Formulas Rules for Posting in VA forum  Request Expert's Reply ( VA Forum Only )



Board of Directors
Joined: 17 Jul 2014
Posts: 2562
Location: United States (IL)
Concentration: Finance, Economics
GPA: 3.92
WE: General Management (Transportation)

Re: The cost per unit of electricity during a 4 year period is a
[#permalink]
Show Tags
25 Mar 2016, 18:51
bumped again into this question..started to consider some coefficients for units used..but then...considered 6$ as total spent. I believe this is the LCM of 1, 1.5, 1.2, and 2. 1st year  6 units 2nd year  4 units 3rd year  5 units 4th year  3 units
total = 18 units. total $ spent = 24$. 24/18 = 4/3 = 1.33



Target Test Prep Representative
Status: Founder & CEO
Affiliations: Target Test Prep
Joined: 14 Oct 2015
Posts: 5356
Location: United States (CA)

Re: The cost per unit of electricity during a 4 year period is a
[#permalink]
Show Tags
15 Mar 2018, 10:09
Safal wrote: The cost per unit of electricity during a 4 year period is as follows:
Year 1, $1 per unit; Year 2, $1.5 per unit; Year 3, $1.2 per unit; Year 4, $2 per unit.
If a factory spent equal dollars on electricity each year, what was the average cost of a unit of electricity during the 4 year period?
A. $1.333 B. $1.250 C. $1.425 D. $1.175 E. $1.500 We can assume the factory spent $18 a year on electricity. Thus, it used Year 1: 18 units of electricity Year 2: 12 units of electricity Year 3: 15 units of electricity Year 2: 9 units of electricity Therefore, the average cost per unit is: (4 x 18)/(18 + 12 + 15 + 9) 72/54 4/3 1.333 Answer: A
_________________
5star rated online GMAT quant self study course See why Target Test Prep is the top rated GMAT quant course on GMAT Club. Read Our Reviews




Re: The cost per unit of electricity during a 4 year period is a
[#permalink]
15 Mar 2018, 10:09






