• NEW! FREE Beat The GMAT Quizzes
Hundreds of Questions Highly Detailed Reporting Expert Explanations
• 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 PRACTICE GMAT EXAMS Earn 10 Points Per Post Earn 10 Points Per Thanks Earn 10 Points Per Upvote ## twice as many omelettes tagged by: Brent@GMATPrepNow ##### This topic has 8 expert replies and 5 member replies ### GMAT/MBA Expert ## twice as many omelettes 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. â€“Lord Buddha Sanjeev K Saxena Quantitative Instructor The Princeton Review - Manya Abroad Lucknow-226001 www.manyagroup.com 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. ### Top Member Master | Next Rank: 500 Posts Joined 15 Oct 2009 Posted: 331 messages Upvotes: 27 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 ### GMAT/MBA Expert GMAT Instructor Joined 08 Dec 2008 Posted: 13046 messages Followed by: 1252 members Upvotes: 5254 GMAT Score: 770 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 â€“ Creator of GMATPrepNow.com Use my video course along with 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 GMAT Prep Now's comprehensive video course can be used in conjunction with Beat The GMATâ€™s FREE 60-Day Study Guide and reach your target score in 2 months! Master | Next Rank: 500 Posts Joined 07 Jun 2014 Posted: 126 messages Upvotes: 3 Brent, I think it should be 15.Opt-B. ### GMAT/MBA Expert GMAT Instructor Joined 25 May 2010 Posted: 15387 messages Followed by: 1872 members Upvotes: 13060 GMAT Score: 790 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 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 08 Dec 2008 Posted: 13046 messages Followed by: 1252 members Upvotes: 5254 GMAT Score: 770 sandipgumtya wrote: Brent, I think it should be 15.Opt-B. Good catch! I edited my answer - thanks. Cheers, Brent _________________ Brent Hanneson â€“ Creator of GMATPrepNow.com Use my video course along with Sign up for free Question of the Day emails And check out all of these free resources GMAT Prep Now's comprehensive video course can be used in conjunction with Beat The GMATâ€™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 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. ### GMAT/MBA Expert GMAT Instructor Joined 25 May 2010 Posted: 15387 messages Followed by: 1872 members Upvotes: 13060 GMAT Score: 790 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 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: 82 members Upvotes: 267 GMAT Score: 760 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. _________________ The mind is everything. What you think you become. â€“Lord Buddha Sanjeev K Saxena Quantitative Instructor The Princeton Review - Manya Abroad Lucknow-226001 www.manyagroup.com 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 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. Junior | Next Rank: 30 Posts Joined 16 Jan 2017 Posted: 24 messages 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 Karins 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? ### GMAT/MBA Expert GMAT Instructor Joined 08 Dec 2008 Posted: 13046 messages Followed by: 1252 members Upvotes: 5254 GMAT Score: 770 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 Karins 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 â€“ Creator of GMATPrepNow.com Use my video course along with Sign up for free Question of the Day emails And check out all of these free resources GMAT Prep Now's comprehensive video course can be used in conjunction with Beat The GMATâ€™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: 497 members Upvotes: 2867 GMAT Score: 800 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 ### GMAT/MBA Expert GMAT Instructor Joined 09 Apr 2015 Posted: 1465 messages Followed by: 19 members Upvotes: 39 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 • 5-Day Free Trial 5-day free, full-access trial TTP Quant Available with Beat the GMAT members only code • Free Practice Test & Review How would you score if you took the GMAT Available with Beat the GMAT members only code • Magoosh Study with Magoosh GMAT prep Available with Beat the GMAT members only code • Award-winning private GMAT tutoring Register now and save up to$200

Available with Beat the GMAT members only code

• FREE GMAT Exam
Know how you'd score today for \$0

Available with Beat the GMAT members only code

• Free Trial & Practice Exam
BEAT THE GMAT EXCLUSIVE

Available with Beat the GMAT members only code

• Get 300+ Practice Questions
25 Video lessons and 6 Webinars for FREE

Available with Beat the GMAT members only code

• Free Veritas GMAT Class
Experience Lesson 1 Live Free

Available with Beat the GMAT members only code

• 5 Day FREE Trial
Study Smarter, Not Harder

Available with Beat the GMAT members only code

• 1 Hour Free
BEAT THE GMAT EXCLUSIVE

Available with Beat the GMAT members only code

### Top First Responders*

1 Ian Stewart 44 first replies
2 Jay@ManhattanReview 35 first replies
3 Brent@GMATPrepNow 34 first replies
4 Scott@TargetTestPrep 31 first replies
5 GMATGuruNY 18 first replies
* Only counts replies to topics started in last 30 days
See More Top Beat The GMAT Members

### Most Active Experts

1 Scott@TargetTestPrep

Target Test Prep

129 posts
2 Max@Math Revolution

Math Revolution

89 posts
3 Ian Stewart

GMATiX Teacher

53 posts
4 Brent@GMATPrepNow

GMAT Prep Now Teacher

50 posts
5 Jay@ManhattanReview

Manhattan Review

35 posts
See More Top Beat The GMAT Experts