Register    Login    Search    Rss Feeds

Forums Home » Ask An Instructor » GMAT Math » GMAT Prep Math


 Page 1 of 1 [ 3 posts ] 



  Print view Print view Previous topic Previous topic | Next topic Next topic
 

a certain meter records voltage

Author Message
urooj.khan
 Post subject: a certain meter records voltage
 Post Posted: Sat Jun 13, 2009 6:50 pm 
Offline


Posts: 17
a certain meter records voltage between 0 and 10 volts, inclusive. if the average value of 3 recordings from the meter was 8 volts, what was the smallest possible recording in volts?

A) 2
B) 3
C) 4
D) 5
E) 6
Top 
stock.mojo11
 Post subject: Re: a certain meter records voltage
 Post Posted: Sun Jun 14, 2009 10:28 am 
Offline
Forum Guests


Posts: 43
urooj.khan wrote:
a certain meter records voltage between 0 and 10 volts, inclusive. if the average value of 3 recordings from the meter was 8 volts, what was the smallest possible recording in volts?

A) 2
B) 3
C) 4
D) 5
E) 6


(v1+v2+v3)/3=8

v1+v2+v3=24

For any one to be min, the other two must be max.

max for v =10, If v1 is min and v2,v3 are max

v1= 24-20=4
Top 
RonPurewal
 Post subject: Re: a certain meter records voltage
 Post Posted: Mon Jun 15, 2009 10:53 pm 
Offline
ManhattanGMAT Staff


Posts: 6756
the solution above is good.

what's more important than this particular solution, as usual, is the TAKEAWAY that you can get from it.

TAKEAWAY:

when you have numbers with a fixed sum or product:

if you want to MINIMIZE A QUANTITY, then you must MAXIMIZE ALL OTHER QUANTITIES in the sum or product.

if you want to MAXIMIZE A QUANTITY, then you must MINIMIZE ALL OTHER QUANTITIES in the sum or product.

if you make this realization, then this problem is simple:
you're trying to minimize one voltage reading.
this means that you should maximize the other readings: make two of them 10 volts each.
the third reading is thus 24 - 10 - 10, or 4 volts.
Top 
Display posts from previous:  Sort by  
 
 Page 1 of 1 [ 3 posts ] 





Who is online

Users browsing this forum: No registered users and 1 guest

 
 

 
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to: