In an electric circuit, two resistors with resistances x and y are : GMAT Problem Solving (PS)
Check GMAT Club App Tracker for the Latest School Decision Releases http://gmatclub.com/AppTrack

It is currently 11 Dec 2016, 02:42
GMAT Club Tests

Close

GMAT Club Daily Prep

Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Close

Request Expert Reply

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

In an electric circuit, two resistors with resistances x and y are

  post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

1 KUDOS received
Manager
Manager
avatar
Joined: 27 Mar 2008
Posts: 81
Followers: 1

Kudos [?]: 93 [1] , given: 0

In an electric circuit, two resistors with resistances x and y are [#permalink]

Show Tags

New post 20 Aug 2008, 21:33
1
This post received
KUDOS
2
This post was
BOOKMARKED
00:00
A
B
C
D
E

Difficulty:

  25% (medium)

Question Stats:

62% (02:01) correct 38% (01:05) wrong based on 143 sessions

HideShow timer Statistics

In an electric circuit, two resistors with resistances x and y are connected in parallel. In this case, if r is the combined resistance of these two resistors, then the reciprocal of r is equal to the sum of the reciprocals of x and y. What is r in terms of x and y?

(A) xy
(B) x + y
(C) 1/(x + y)
(D) xy/(x + y)
(E) (x + y)/xy

OPEN DISCUSSION OF THIS QUESTION IS HERE: in-an-electric-circuit-two-resistors-with-resistances-x-and-144899.html
[Reveal] Spoiler: OA
Intern
Intern
avatar
Joined: 19 Aug 2008
Posts: 2
Followers: 0

Kudos [?]: 0 [0], given: 0

Re: In an electric circuit, two resistors with resistances x and y are [#permalink]

Show Tags

New post 20 Aug 2008, 22:05
its simple ..

1/r=1/x+1/y
1/r=x+y/xy
r=xy/x+y
1 KUDOS received
Manager
Manager
avatar
Joined: 27 Mar 2008
Posts: 81
Followers: 1

Kudos [?]: 93 [1] , given: 0

Re: In an electric circuit, two resistors with resistances x and y are [#permalink]

Show Tags

New post 21 Aug 2008, 10:51
1
This post received
KUDOS
The beginning of question is confusing...

two resistors with resistances x and y are connected in parallel. In this case, if r is the combined resistance of these two resistors


Does this have anything to do w/ the questions b/c to me, it seems the latter is purpose of question..
Manager
Manager
User avatar
Joined: 18 Jan 2008
Posts: 221
Schools: The School that shall not be named
Followers: 3

Kudos [?]: 25 [0], given: 0

Re: In an electric circuit, two resistors with resistances x and y are [#permalink]

Show Tags

New post 21 Aug 2008, 11:01
droopy57 wrote:
The beginning of question is confusing...

two resistors with resistances x and y are connected in parallel. In this case, if r is the combined resistance of these two resistors


Does this have anything to do w/ the questions b/c to me, it seems the latter is purpose of question..


It just means r = value of (x//y)
Basically... this is EE101 of finding the equivalent resistor value. :-D
1/r = 1/x + 1/y is the starting equation
1/r = (x+y)/xy
and r = xy/(x+y)
_________________

明日やろうばかやろう

24 wrote:
Your East Coast bias is worse than ESPN.

1 KUDOS received
SVP
SVP
User avatar
Joined: 30 Apr 2008
Posts: 1887
Location: Oklahoma City
Schools: Hard Knocks
Followers: 40

Kudos [?]: 565 [1] , given: 32

Re: In an electric circuit, two resistors with resistances x and y are [#permalink]

Show Tags

New post 21 Aug 2008, 11:08
1
This post received
KUDOS
That's great for all of those EE's out there...oh wait, they're actually a small % of MBA seekers.

For the rest of us

reciprocal of x = 1/x
reciprocal of r = 1/r
reciprocal of y = 1/y

1/r = 1/x + 1/y

To get the same denominator
\(\frac{1}{r} = \frac{y}{y}*\frac{1}{x} + \frac{x}{x}*\frac{1}{y}\)

becomes

\(\frac{1}{r} = \frac{y}{xy} + \frac{x}{xy}\)

\(\frac{1}{r} = \frac{X + y}{xy}\)

Now you can get rid of the fraction with \(r\) by cross multiplying
r * (x+y) = 1*xy
and then dividing to get r alone
r = xy/x+y
fatb wrote:
droopy57 wrote:
The beginning of question is confusing...

two resistors with resistances x and y are connected in parallel. In this case, if r is the combined resistance of these two resistors


Does this have anything to do w/ the questions b/c to me, it seems the latter is purpose of question..


It just means r = value of (x//y)
Basically... this is EE101 of finding the equivalent resistor value. :-D
1/r = 1/x + 1/y is the starting equation
1/r = (x+y)/xy
and r = xy/(x+y)

_________________

------------------------------------
J Allen Morris
**I'm pretty sure I'm right, but then again, I'm just a guy with his head up his a$$.

GMAT Club Premium Membership - big benefits and savings

Manager
Manager
avatar
Joined: 27 Mar 2008
Posts: 81
Followers: 1

Kudos [?]: 93 [0], given: 0

Re: In an electric circuit, two resistors with resistances x and y are [#permalink]

Show Tags

New post 21 Aug 2008, 11:51
ok. i see where i went wrong. i did this:

1/r = 2/ x+y

wasn't thinking that i couldnt combine unless it was like terms...
GMAT Club Legend
GMAT Club Legend
User avatar
Joined: 09 Sep 2013
Posts: 12908
Followers: 563

Kudos [?]: 158 [0], given: 0

Premium Member
Re: In an electric circuit, two resistors with resistances x and y are [#permalink]

Show Tags

New post 13 Mar 2015, 10:55
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

Expert Post
EMPOWERgmat Instructor
User avatar
Status: GMAT Assassin/Co-Founder
Affiliations: EMPOWERgmat
Joined: 19 Dec 2014
Posts: 8019
Location: United States (CA)
GMAT 1: 800 Q51 V49
GRE 1: 340 Q170 V170
Followers: 363

Kudos [?]: 2377 [0], given: 163

Re: In an electric circuit, two resistors with resistances x and y are [#permalink]

Show Tags

New post 13 Mar 2015, 11:18
Hi All,

While this question looks a little "crazy", it can be solved with TESTing VALUES.

We're told that the reciprocal of R is equal to the SUM of the reciprocals of X and Y. This means….

1/R = 1/X + 1/Y

We're asked for the value of R in terms of X and Y

IF...
X = 2 and Y = 3, then we have…

1/R = 1/2 + 1/3

1/R = 3/6 + 2/6 = 5/6

R = 6/5

So we need an answer that = 6/5 when X = 2 and Y = 3.

The only answer that matches is
[Reveal] Spoiler:
D


GMAT assassins aren't born, they're made,
Rich
_________________

Rich Cohen

Co-Founder & GMAT Assassin

Special Offer: Save $75 + GMAT Club Tests

60-point improvement guarantee
www.empowergmat.com/

***********************Select EMPOWERgmat Courses now include ALL 6 Official GMAC CATs!***********************

GMAT Club Legend
GMAT Club Legend
User avatar
Joined: 09 Sep 2013
Posts: 12908
Followers: 563

Kudos [?]: 158 [0], given: 0

Premium Member
Re: In an electric circuit, two resistors with resistances x and y are [#permalink]

Show Tags

New post 23 Apr 2016, 09:51
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

Expert Post
Math Expert
User avatar
Joined: 02 Sep 2009
Posts: 35951
Followers: 6867

Kudos [?]: 90129 [0], given: 10418

Re: In an electric circuit, two resistors with resistances x and y are [#permalink]

Show Tags

New post 24 Apr 2016, 02:36
droopy57 wrote:
In an electric circuit, two resistors with resistances x and y are connected in parallel. In this case, if r is the combined resistance of these two resistors, then the reciprocal of r is equal to the sum of the reciprocals of x and y. What is r in terms of x and y?

(A) xy
(B) x + y
(C) 1/(x + y)
(D) xy/(x + y)
(E) (x + y)/xy


The wording is a bit confusing, though basically we are told that 1/r = 1/x + 1/y, from which it follows that r=xy/(x + y).

Answer: D.

OPEN DISCUSSION OF THIS QUESTION IS HERE: in-an-electric-circuit-two-resistors-with-resistances-x-and-144899.html
_________________

New to the Math Forum?
Please read this: 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?
Extra-hard Quant Tests with Brilliant Analytics

Re: In an electric circuit, two resistors with resistances x and y are   [#permalink] 24 Apr 2016, 02:36
    Similar topics Author Replies Last post
Similar
Topics:
3 Experts publish their posts in the topic If two resistors, A(R1) and B(R2) stand in parallel with each other in MathRevolution 3 12 Jan 2016, 17:52
12 Experts publish their posts in the topic In an electric circuit, two resistors with resistances x and Walkabout 16 29 Dec 2012, 04:39
4 Experts publish their posts in the topic If two of the four expressions x + y , x + 5y , x - y , and 5x - y are nifoui 4 21 Mar 2010, 09:53
10 Experts publish their posts in the topic If two of the four expressions x+y, x+5y, x-y, 5x+y are chos DenisSh 8 04 Oct 2009, 00:57
6 Experts publish their posts in the topic If two of the four expressions x+y, x+5y, x-y, and 5x-y are GMATBLACKBELT 12 24 Oct 2007, 21:35
Display posts from previous: Sort by

In an electric circuit, two resistors with resistances x and y are

  post reply Question banks Downloads My Bookmarks Reviews Important topics  


GMAT Club MBA Forum Home| About| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group and phpBB SEO

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.