How to solve work and rates problem in GMAT

Work Rate ProblemsCarefully go through the following question types. These are the standard work rate problems that you would encounter in your GMAT Exam.

Working Together

In questions where individuals work at different speeds, we typically need to add their separate rates together. Make sure you keep your units straight. This doesn’t mean wasting time and writing each and every one out, but rather simply recognizing their existence. Note that when working together, the total time to complete the same task will be less than BOTH of the individual rates, but not necessarily in proportion. Nor, are you averaging or adding the given times taken. You must add rates.

Q) A worker can load 1 full truck in 6 hours. A second worker can load the same truck in 7 hours. If both workers load one truck simultaneously while maintaining their constant rates, approximately how long, in hours, will it take them to fill 1 truck?

A. 0.15
B. 0.31
C. 2.47
D. 3.23
E. 3.25

The rate of worker #1 is 1 truck/6 hours. This can also be 1/6 trucks/1 hour. The rate of worker #2 is 1/7. When together, they will complete 1/6 + 1/7 trucks/ 1 hour.

1/6 + 1/7 = 6/42 + 7/42 = 13/42 trucks/1 hour. Remember the question is asking for the number of hours to fill 1 truck, NOT the number of trucks completed in 1 hour. To find this, we find the reciprocal of 13/42.

42/13 hours/truck = 3 3/13 hours/truck.

At this point, we may not be able to decide between (D) or (E). However, the decimal is important. Because the denominator is 13, we know the decimal cannot equal .25. We can also see that 3/12 will yield .25, so 3/13 will be slightly lower. Choice (E).

Relative Velocity

Planes, trains and automobiles. Sometimes walking. Objects moving at given speeds on the GMAT usually travel toward or away from each other. When moving at an angle, we may be looking at a geometry question. If moving toward or away from each other, we can add their speeds to see their relative velocities. If moving in the same direction, we instead subtract their speeds to find the relative velocity. Again, be careful of units.

Q) Train A traveling at 60 m/hr leaves New York for Dallas at 6 P.M. Train B traveling at 90 m/hr also leaves New York for Dallas at 9 P.M. Train C leaves Dallas for New York at 9 P.M. If all three trains meet at the same time between New York and Dallas, what is the speed of Train C if the distance between Dallas and New York is 1260 miles?

A. 60 m/hr
B. 90 m/hr
C. 120 m/hr
D. 135 m/hr
E. 180 m/hr

Relative to Train A, Train B’s velocity is 30 m/hr. This means that B will gain on A at a rate of 30 miles every hour. In the three hours from 6pm to 9pm, A gets to mile marker 180. To catch up the 180 miles, it will take Train B 6 hours. So when they all meet up, the time will be 3am, and they will be at mile marker 540. Notice that:

Train A = 9 hours at 60 miles/hour = 540 miles
Train B = 6 hours at 90 miles/hour = 540 miles
We can now tackle Train C, which has traveled the same time as B (6 hours), and traveled (1260 – 540) miles.
Rate of Train C = 720 miles/ 6 hours = 120 miles/hour. Choice (C).

Man Hours

Many times you may be asked to calculate the number of workers would be need to complete a certain task. Keep in mind that the number of workers (at the same efficiency) is inversely proportional to the amount of time it takes one to complete a given task. It may help consider the unit man-hours as the multiplication between workers and time, which is then compared to the work completed. For example:

Q) Three plows working at identical constant rates can clear 123 ft of snow per minute. At this rate, how much snow could 8 plows remove in 5 minutes?

A. 328
B. 984
C. 1,640
D. 16,400
E. 131,200

Instead of man-hours, here we want to interact plow-minutes. Feet and minutes are already compared, so all we have to is add “plows” to the expression. If we divide 123 ft/min by 3 plows, we get:

123 ft/minute/3 plows = 41 ft/plow-minute

At this rate, if we want to increase minutes to 5 and plows to 8, we can simply insert these into the existing rate. Note the absolute rate does not change, since we are multiplying top and bottom by 40, so the value is constant.

41*40 feet / 40 plow-minutes = 1640 feet / 40 plow-minutes.

Choice (C).

Author : 

Grockit, an online test prep game, is the smartest way to study for your test. It's adaptive, fun and finds the right teacher for you. Grockit’s analytic capabilities and adaptive technology identifies students' strengths and weaknesses, focusing the student's study time.  Students can practice in adaptive solo games, play social learning games with peers, and work with experts that match their specific needs.

Top 31 MBA Programs + Analysis of 24 Industries (United States)

We analyze the MBA Curriculum, Class Profile, Total Cost and Post-MBA Salary of Top 31 MBA programs in the US.

+ Industry Trends

+ Future of Aerospace, Agriculture, Artificial Intelligence (AI), Automobile, Clean Tech, Education, Energy, Fashion, Financial Services, Insurance, FinTech, Government, Healthcare, Life Sciences, Military, Manufacturing, Maritime, Media/Advertising, Technology, Tourism, Trade, Transportation and Logistics, Virtual Reality (VR), and Augmented Reality (AR).

Pages: 327


"I have not reviewed many books for MBA Admission consulting companies but doing it now to give all applicants a brief idea on what the book covers. The book includes 31 top MBA programs - almost all the top schools you have heard or considering for your MBA application. Each chapter is categorized by US States where there is at least one top MBA program. So you have California and Massachusetts with the most number of MBA programs and several states with one top program (Washington, Minnesota, Washington D.C., Connecticut, Virginia, and Maryland) and other states with two to three MBA programs. The book focuses on four aspects of an MBA program - curriculum, cost, class profile and post-MBA salary. For me, the breakdown of the cost and post-MBA industry was useful to make my decision on selecting the top 5 programs for 2017-18. It is a fascinating read in an industry where consultants overprice for their expertise. I recently bought a 30-page guide for $49. Compared to the obvious observation in that book, the 300+ page, MBA in US - the Ultimate guide is a goldmine of information and analysis." - Verified Purchase (21st June 2017)

"I bought the ultimate guide after a friend recommended it for me. The guide covers a lot of ground on the history of each prominent US states and goes into the reasons why a certain industry emerged from each state. In addition to the analysis of the economy, trends and expected changes in the next 5 years, the book features top MBA programs in each state with an extensive study of its curriculum. Ultimate guide is an essential reference book for MBA Applicants if they want to shortlist MBA programs based on value and cost, and not just ranking. " - Verified Purchase (14th June 2017)

"Should be a required reading before applying for an MBA. School events and MBA Tours are PR events disguised as a Q&A. On the contrary, the book is an unbiased analysis of each Top MBA program in the US supported by a large dataset and historical context on each industry. The guide builds a case for indstries that are likely to emerge as favourite for MBA graduates. Thorough and a valuable book." - Verified Purchase (15th June 2017)

"What I liked: The breadth of the information. Some of my favorite nonfiction books have taken the same approach as the ultimate guide have - cover background information in-depth. In the book, the author uses parallel threads to demonstrate the history of the state and the rise of industries. Will make you think how schools thrive based on the policy set by the state. California's obsession with Technology has revolutionized how we do Business and changed post-MBA trends. Many MBA applicants will be consulting or doing marketing for a Technology company. That is one key finding from the book. The latest development in AI, FinTech, and Automation is an additional context that I found valuable in the book.

Very informative. I would recommend that you read the book at least once in chronological order before using Table of Contents." - Verified Purchase (2nd July 2017)

Download How to Choose the Best MBA in US: The Ultimate Guide
(2018 Entering Class)

Get F1GMAT's Newsletters (Best in the Industry)
Included in the Newsletter:

  • Ranking Analysis
  • Post-MBA Salary Trends
  • Post-MBA Job Function & Industry Analysis
  • Post-MBA City Review
  • MBA Application Essay Tips
  • School Specific Essay Tips
  • GMAT Preparation Tips
  • MBA Admission Interview Tips
  • School Specific Interview Tips
  • Funding Guidance and
  • Special Consultation Service (only for Subscribers)

Subscribe to F1GMAT's Newsletter