• NEW! FREE Beat The GMAT Quizzes
    NEW! FREE Beat The GMAT Quizzes
    NEW! FREE Beat The GMAT Quizzes
    Hundreds of Questions Highly Detailed Reporting Expert Explanations TAKE A FREE GMAT QUIZ
  • 7 CATs FREE!
    If you earn 100 Forum Points

    Engage in the Beat The GMAT forums to earn
    100 points for $49 worth of Veritas practice GMATs FREE

    Veritas Prep
    VERITAS PRACTICE GMAT EXAMS
    Earn 10 Points Per Post
    Earn 10 Points Per Thanks
    Earn 10 Points Per Upvote
    REDEEM NOW

twice as many omelettes

This topic has 8 expert replies and 5 member replies

GMAT/MBA Expert

twice as many omelettes

Post
Chef Karin can prepare twice as many omelettes in 50 minutes as Chef Zibo could prepare in 30 minutes. If both chefs working together for 10 minutes could prepare 11 omelettes, how many omelettes could Chef Karin prepare working alone for 25 minutes?
A. 12
B. 15
C. 18
D. 22
E. 25

Made Up!

_________________
The mind is everything. What you think you become. –Lord Buddha



Sanjeev K Saxena
Quantitative Instructor
The Princeton Review - Manya Abroad
Lucknow-226001

www.manyagroup.com

  • +1 Upvote Post
  • Quote
  • Flag
Free GMAT Practice Test How can you improve your test score if you don't know your baseline score? Take a free online practice exam. Get started on achieving your dream score today! Sign up now.
Master | Next Rank: 500 Posts Default Avatar
Joined
15 Oct 2009
Posted:
329 messages
Upvotes:
27
Post
sanju09 wrote:
Chef Karin can prepare twice as many omelettes in 50 minutes as Chef Zibo could prepare in 30 minutes. If both chefs working together for 10 minutes could prepare 11 omelettes, how many omelettes could Chef Karin prepare working alone for 25 minutes?
A. 12
B. 15
C. 18
D. 22
E. 25

Made Up!
15

  • +1 Upvote Post
  • Quote
  • Flag

GMAT/MBA Expert

Post
sanju09 wrote:
Chef Karin can prepare twice as many omelettes in 50 minutes as Chef Zibo could prepare in 30 minutes. If both chefs working together for 10 minutes could prepare 11 omelettes, how many omelettes could Chef Karin prepare working alone for 25 minutes?

A. 12
B. 15
C. 18
D. 22
E. 25
Nice question, Sanju!

One approach is to determine the RELATIVE RATES of Karin and Zibo.

Chef Karin can prepare twice as many omelettes in 50 minutes as Chef Zibo could prepare in 30 minutes.
Let's arbitrarily say that Chef Zibo can prepare 1 omelette in 30 minutes
This means that Chef Karin can prepare 2 omelettes in 50 minutes
NOTE: Since we have different times (30 min and 50 min), it's hard to compare rates. So, let's find a NICE timeframe where we can compare both chefs.

The LEAST COMMON MULTIPLE of 30 and 50 is 150, so let's see how many omelettes each chef can make in 150 minutes
- If Chef Zibo can prepare 1 omelette in 30 minutes, then he/she can prepare 5 omelettes in 150 minutes
- If Chef Karin can prepare 2 omelette in 50 minutes, then he/she can prepare 6 omelettes in 150 minutes

So, within the same 150-minute timeframe, Chef Zibo can prepare 5 omelettes and Chef Karin can prepare 6 omelettes.
In other words, for EVERY 11 omelettes that get produced TOGETHER, Chef Zibo prepares 5 omelettes and Chef Karin prepares 6 omelettes.

...both chefs working together for 10 minutes could prepare 11 omelettes
PERFECT.
This means that, in 10 minutes, Chef Zibo prepares 5 omelettes and Chef Karin prepares 6 omelettes.
If Chef Karin can produce 6 omelettes in 10 minutes, he/she can produce 12 omelettes in 20 minutes, and 15 omelettes in 25 minutes.

Answer: B

Cheers,
Brent

_________________
Brent Hanneson – Creator of GMATPrepNow.com
Use my video course along with Beat The GMAT's free 60-Day Study Guide

Sign up for free Question of the Day emails
And check out all of these free resources



Last edited by Brent@GMATPrepNow on Fri Feb 20, 2015 6:53 am; edited 1 time in total

  • +1 Upvote Post
  • Quote
  • Flag
GMAT Prep Now's comprehensive video course can be used in conjunction with Beat The GMAT’s FREE 60-Day Study Guide and reach your target score in 2 months!
Master | Next Rank: 500 Posts Default Avatar
Joined
07 Jun 2014
Posted:
126 messages
Upvotes:
3
Post
Brent,
I think it should be 15.Opt-B.

  • +1 Upvote Post
  • Quote
  • Flag

GMAT/MBA Expert

Post
sanju09 wrote:
Chef Karin can prepare twice as many omelettes in 50 minutes as Chef Zibo could prepare in 30 minutes. If both chefs working together for 10 minutes could prepare 11 omelettes, how many omelettes could Chef Karin prepare working alone for 25 minutes?
A. 12
B. 15
C. 18
D. 22
E. 25
Let K = Chef Karin and Z = Chef Zibo.

Chef Karin can prepare twice as many omelettes in 50 minutes as Chef Zibo could prepare in 30 minutes.
Let's say Z produces 1 omelet in 30 minutes, implying that K produces 2 omelets in 50 minutes.
At a rate of 1 omelet per 30 minutes, the number of omelets produced by Z in 150 minutes = 5.
At a rate of 2 omelets per 50 minutes, the number of omelets produced by K in 150 minutes = 6.
Thus, if Z and K work together for 150 minutes, the total number of omelets produced = 5+6 = 11.
Of these 11 omelets, K produces 6.
Implication:
When Z and K work together, K produces 6/11 of the work.

Both chefs working together for 10 minutes could prepare 11 omelettes.
Thus, the combined rate for Z and K working together = w/t = 11/10 omelets per minute.
Since K produces 6/11 of the work, K's rate alone - (6/11)(11/10) = 3/5 omelet per minute.

Result:
At a rate of 3/5 omelet per minute, the number of omelets produced by K in 25 minutes = r*t = (3/5)(25) = 15 omelets.

The correct answer is B.

_________________
Mitch Hunt
Private Tutor for the GMAT and GRE
GMATGuruNY@gmail.com

If you find one of my posts helpful, please take a moment to click on the "UPVOTE" icon.

Available for tutoring in NYC and long-distance.
For more information, please email me at GMATGuruNY@gmail.com.
Student Review #1
Student Review #2
Student Review #3

  • +1 Upvote Post
  • Quote
  • Flag
Free GMAT Practice Test How can you improve your test score if you don't know your baseline score? Take a free online practice exam. Get started on achieving your dream score today! Sign up now.

GMAT/MBA Expert

Post
sandipgumtya wrote:
Brent,
I think it should be 15.Opt-B.
Good catch!
I edited my answer - thanks.

Cheers,
Brent

_________________
Brent Hanneson – Creator of GMATPrepNow.com
Use my video course along with Beat The GMAT's free 60-Day Study Guide

Sign up for free Question of the Day emails
And check out all of these free resources

  • +1 Upvote Post
  • Quote
  • Flag
GMAT Prep Now's comprehensive video course can be used in conjunction with Beat The GMAT’s FREE 60-Day Study Guide and reach your target score in 2 months!
Master | Next Rank: 500 Posts
Joined
27 Apr 2014
Posted:
269 messages
Followed by:
5 members
Upvotes:
8
Facebook Logo
Post
I did it in the below manner:-

Rate * time = work done

Z = Zibo's rate
K = karin's rate
x = omelettes by z

For Z=> Z * 30/60 = x => Z = 2x (1)
For K => K * 50/60 = 2x => K = 12/5x (2)

Now combine: (Z+K)*10/60 = 11 => Z+K = 66 (3)

Solve for x => x = 15

For K 's rate , put value of x in (2) => K = 36
Now K*25/60 =?
36*25/60 = 15 omelettes by K alone in 25 mins.

  • +1 Upvote Post
  • Quote
  • Flag

GMAT/MBA Expert

Post
sanju09 wrote:
Chef Karin can prepare twice as many omelettes in 50 minutes as Chef Zibo could prepare in 30 minutes. If both chefs working together for 10 minutes could prepare 11 omelettes, how many omelettes could Chef Karin prepare working alone for 25 minutes?
A. 12
B. 15
C. 18
D. 22
E. 25
An alternate approach is to apply the following formula:
(rate)(time)/work = (rate)(time)/work.

Let K = Chef Karin's rate and Z = Chef Zibo's rate.

Since K produces twice as many omelets in 50 minutes as Z produces in 30 minutes, we get:
(K)(50)/2w = (Z)(30)/w
25K = 30Z
Z = (25/30)K
Z = (5/6)K.

Thus, when K and Z work together, their combined rate = K + Z = K + (5/6)K = (11/6)K.
Since this combined rate takes 10 minutes to produce 11 omelets, we get:
(11/6)K * 10 = 11
K = 6/10
K = 3/5.

At a rate of 3/5 omelet per minute, the number of omelets produced by K in 25 minutes = rt = (3/5)(25) = 15.

The correct answer is B.

_________________
Mitch Hunt
Private Tutor for the GMAT and GRE
GMATGuruNY@gmail.com

If you find one of my posts helpful, please take a moment to click on the "UPVOTE" icon.

Available for tutoring in NYC and long-distance.
For more information, please email me at GMATGuruNY@gmail.com.
Student Review #1
Student Review #2
Student Review #3

  • +1 Upvote Post
  • Quote
  • Flag
Free GMAT Practice Test How can you improve your test score if you don't know your baseline score? Take a free online practice exam. Get started on achieving your dream score today! Sign up now.

GMAT/MBA Expert

GMAT Instructor
Joined
21 Jan 2009
Posted:
3650 messages
Followed by:
81 members
Upvotes:
267
GMAT Score:
760
Facebook Logo
Post
Great replies! Thanks Brent for the back-up.

Rates can best be compared if we set the work equal. In that case, ratio in individual rates is equal to the reciprocal of ratio in individual times taken.

To compare, we can say that if K prepares 2 omelettes in 50 minutes, then Z would prepare i omelette in 30 minutes; or if K prepares 1 omelette in 25 minutes, then Z would prepare i omelette in 30 minutes.

Hence, the ratio in their rates is, i.e. K to J is 30:25 or 6:5.

It means that in a given time, if K prepares 6, then Z prepares 5, together they could prepare 6 + 5 = 11 in the given time, which is given to be 10 minutes in the question. Using this we can say that K alone can prepare

6 omelettes in 10 minutes

6/10 omelettes in 1 minute

(6/10) X 25 = 15 omelettes in 25 minutes.

It's (B) really.

Smile

_________________
The mind is everything. What you think you become. –Lord Buddha



Sanjeev K Saxena
Quantitative Instructor
The Princeton Review - Manya Abroad
Lucknow-226001

www.manyagroup.com

  • +1 Upvote Post
  • Quote
  • Flag
Free GMAT Practice Test How can you improve your test score if you don't know your baseline score? Take a free online practice exam. Get started on achieving your dream score today! Sign up now.
Newbie | Next Rank: 10 Posts
Joined
11 Aug 2015
Posted:
4 messages
Upvotes:
2
Facebook Logo
Post
I did the question in the below method.

K makes 2x omelette in 50 mins then in 1 min = 2x/50
Z makes x omelette in 30 mins then in 1 min = x/30
combined they make 11 omelette in 10 mins so in 1 min = 1.1

We know 1.1 = 2x/50+x/30 = 110x/1500.

Cancelling out the constants gives us x = 15.

so 2x = 30 and 25mins is half of 50 mins so answers is 15 omelette in 25mins.

  • +1 Upvote Post
  • Quote
  • Flag
Junior | Next Rank: 30 Posts
Joined
16 Jan 2017
Posted:
24 messages
Facebook Logo
Post
Brent!

Can you please explain why you took the individual rate of Karen of 6/150min and applied it to the combined rate to find Karin`s output in 25 min? Why you did not do the below

Karin prep 6 in 150
then she prep X in 25
150x=150
x=1

What did I do wrong here?

  • +1 Upvote Post
  • Quote
  • Flag

GMAT/MBA Expert

Post
Zoser wrote:
Brent!

Can you please explain why you took the individual rate of Karen of 6/150min and applied it to the combined rate to find Karin`s output in 25 min? Why you did not do the below

Karin prep 6 in 150
then she prep X in 25
150x=150
x=1

What did I do wrong here?
I think you may have misread the information that says "Chef Karin can prepare twice as many omelettes in 50 minutes as Chef Zibo"

I think you read it as "Chef Karin can prepare two omelettes in 50 minutes..."

_________________
Brent Hanneson – Creator of GMATPrepNow.com
Use my video course along with Beat The GMAT's free 60-Day Study Guide

Sign up for free Question of the Day emails
And check out all of these free resources

  • +1 Upvote Post
  • Quote
  • Flag
GMAT Prep Now's comprehensive video course can be used in conjunction with Beat The GMAT’s FREE 60-Day Study Guide and reach your target score in 2 months!

GMAT/MBA Expert

Elite Legendary Member
Joined
23 Jun 2013
Posted:
10197 messages
Followed by:
496 members
Upvotes:
2867
GMAT Score:
800
Most Active Expert
Post
Hi All,

In these types of questions, it often helps to find a basis for comparison based on either "time" or "output." Here, we're given the output of each chef, but for different amounts of time. The LCM of 50 and 30 is 150, so let's see what happens when each chef works for 150 minutes...

Z = can prepare X omelets in 30 minutes
K = can prepare 2X omelets in 50 minutes

Z = can prepare 5X omelets in 150 minutes
K = can prepare 6X omelets in 150 minutes

So, in 150 minutes, the two chefs can prepare a TOTAL of 11X omelets. This is interesting since we're then told that the two chefs can create 11 omelets in 10 minutes (meaning that Z would prepare 5 of omelets while K would prepare 6 of the omelets)....

We're then asked how many omelets K could prepare in 25 minutes. Since K can prepare 6 omelets in 10 minutes, (s)he can prepare 6(2.5) = 15 omelets in 25 minutes.

Final Answer: B

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

_________________
Contact Rich at Rich.C@empowergmat.com

  • +1 Upvote Post
  • Quote
  • Flag

GMAT/MBA Expert

Post
sanju09 wrote:
Chef Karin can prepare twice as many omelettes in 50 minutes as Chef Zibo could prepare in 30 minutes. If both chefs working together for 10 minutes could prepare 11 omelettes, how many omelettes could Chef Karin prepare working alone for 25 minutes?
A. 12
B. 15
C. 18
D. 22
E. 25
We are given that Chef Karin can prepare twice as many omelettes in 50 minutes as Chef Zibo can prepare in 30 minutes. Thus, if we let the rate of Chef Karin = k and the rate of Chef Zibo = z, we can create the following equation:

50k = 2(30z)

50k = 60z

5k = 6z

5k/6 = z

We are also given that both chefs working together for 10 minutes could prepare 11 omelettes. Thus:

(k + z)10 = 11

Next we can substitute 5k/6 for z in the equation (k + z)10 = 11 and we have:

(k + 5k/6)10 = 11

10k + 50k/6 = 11

Multiplying the entire equation by 6, we have:

60k + 50k = 66

110k = 66

k = 66/110 = 6/10 = 3/5

Thus, Chef Karin can prepare (3/5) x 25 = 15 omelets in 25 minutes.

Answer: B

_________________

Jeffrey Miller
Head of GMAT Instruction
jeff@targettestprep.com



See why Target Test Prep is rated 5 out of 5 stars on BEAT the GMAT. Read our reviews

  • +1 Upvote Post
  • Quote
  • Flag
  • Kaplan Test Prep
    Free Practice Test & Review
    How would you score if you took the GMAT

    Available with Beat the GMAT members only code

    MORE DETAILS
    Kaplan Test Prep
  • Magoosh
    Magoosh
    Study with Magoosh GMAT prep

    Available with Beat the GMAT members only code

    MORE DETAILS
    Magoosh
  • Varsity Tutors
    Award-winning private GMAT tutoring
    Register now and save up to $200

    Available with Beat the GMAT members only code

    MORE DETAILS
    Varsity Tutors
  • e-gmat Exclusive Offer
    Get 300+ Practice Questions
    25 Video lessons and 6 Webinars for FREE

    Available with Beat the GMAT members only code

    MORE DETAILS
    e-gmat Exclusive Offer
  • Economist Test Prep
    Free Trial & Practice Exam
    BEAT THE GMAT EXCLUSIVE

    Available with Beat the GMAT members only code

    MORE DETAILS
    Economist Test Prep
  • The Princeton Review
    FREE GMAT Exam
    Know how you'd score today for $0

    Available with Beat the GMAT members only code

    MORE DETAILS
    The Princeton Review
  • Target Test Prep
    5-Day Free Trial
    5-day free, full-access trial TTP Quant

    Available with Beat the GMAT members only code

    MORE DETAILS
    Target Test Prep
  • PrepScholar GMAT
    5 Day FREE Trial
    Study Smarter, Not Harder

    Available with Beat the GMAT members only code

    MORE DETAILS
    PrepScholar GMAT
  • Veritas Prep
    Free Veritas GMAT Class
    Experience Lesson 1 Live Free

    Available with Beat the GMAT members only code

    MORE DETAILS
    Veritas Prep
  • EMPOWERgmat Slider
    1 Hour Free
    BEAT THE GMAT EXCLUSIVE

    Available with Beat the GMAT members only code

    MORE DETAILS
    EMPOWERgmat Slider

Top First Responders*

1 Ian Stewart 50 first replies
2 Brent@GMATPrepNow 37 first replies
3 Jay@ManhattanReview 33 first replies
4 GMATGuruNY 29 first replies
5 ceilidh.erickson 14 first replies
* Only counts replies to topics started in last 30 days
See More Top Beat The GMAT Members

Most Active Experts

1 image description Scott@TargetTestPrep

Target Test Prep

209 posts
2 image description Max@Math Revolution

Math Revolution

92 posts
3 image description Brent@GMATPrepNow

GMAT Prep Now Teacher

79 posts
4 image description Ian Stewart

GMATiX Teacher

57 posts
5 image description GMATGuruNY

The Princeton Review Teacher

49 posts
See More Top Beat The GMAT Experts