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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 ## A worker can load 1 full truck in 6 hours. A second worker.. tagged by: AAPL ##### This topic has 4 expert replies and 0 member replies ### Top Member ## A worker can load 1 full truck in 6 hours. A second worker.. 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 OA is D. First worker rate will be, 1/6 truck per hour. Second worker rate will be, 1/7 truck per hour. Then, their combined rates if they working together will be, 1/T = 1/6+1/7. Then T = (6*7)/(6+7) = 42/13 = 3.23 hours. Is there a strategic approach to this PS question? Can any experts help, please? Thanks! ### GMAT/MBA Expert GMAT Instructor Joined 08 Dec 2008 Posted: 12999 messages Followed by: 1250 members Upvotes: 5254 GMAT Score: 770 Top Reply AAPL wrote: 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 One approach is to assign a nice value to the entire job (of filling a truck) We want a number that works well with the given times (6 hours and 7 hours) 42 is such a number. So, let's say that filling the truck is equivalent to shoveling 42 scoops of dirt into it. A worker (we'll call worker A) can load 1 full truck in 6 hours Rate = output/time = 42 scoops/6 hours = 7 scoops/hour So, worker A's RATE is 7 scoops/hour Worker B) can load 1 full truck in 7 hours Rate = output/time = 42 scoops/7 hours = 6 scoops/hour So, worker B's RATE is 6 scoops/hour So, their COMBINED rate = 7 scoops/hour + 6 scoops/hour = 13 scoops/hour Worker B) Approximately how long, in hours, will it take them to fill 1 truck? Time = output/rate = 42 scoops/13 scoops/hour = 42/13 hours = 3 3/13 hours ASIDE: Notice that 3 3/12 hours = 3.25 hours So, 3 3/13 hours will equal a little less than 3.25 hours Answer: D 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! ### GMAT/MBA Expert Legendary Member Joined 14 Jan 2015 Posted: 2667 messages Followed by: 122 members Upvotes: 1153 GMAT Score: 770 AAPL wrote: 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 OA is D. First worker rate will be, 1/6 truck per hour. Second worker rate will be, 1/7 truck per hour. Then, their combined rates if they working together will be, 1/T = 1/6+1/7. Then T = (6*7)/(6+7) = 42/13 = 3.23 hours. Is there a strategic approach to this PS question? Can any experts help, please? Thanks! Well, if it were the case that we had two people, each of whom could perform a task individually in 6 hours, we know that if they worked together, they'd do the job in half the time, or in 3 hours. So because one of the individuals does the job in 7 hours, the answer has to be a little more than 3, leaving us with just D or E. (My sense is that the GMAT would probably have been a little more artful about its answer choices, allowing you to use logic to determine which was correct without requiring much arithmetic.) _________________ Veritas Prep | GMAT Instructor Veritas Prep Reviews Save$100 off any live Veritas Prep GMAT Course

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### GMAT/MBA Expert

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Hi AAPL,

We're told that A worker can load 1 full truck in 6 hours, a second worker can load the same truck in 7 hours and both workers load one truck simultaneously while maintaining their constant rates. We're asked for the approximate amount of time, in hours, that it will take them to fill 1 truck. This is an example of a standard 'Work Formula' question.

Work = (A)(B)/(A+B) where A and B are the individual times it takes the two entities to complete the task on their own.

Here, the two values would be 6 and 7...

(6)(7)/(6+7) = 42/13 = 3 3/13 hours

Since 3/13 is LESS then 3/12 = 1/4, the correct answer has to be a little less than 3 1/4 hours

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

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Contact Rich at Rich.C@empowergmat.com

### GMAT/MBA Expert

GMAT Instructor
Joined
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AAPL wrote:
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 combined rate of the two workers is 1/7 + 1/6 = 6/42 + 7/42 = 13/42.

Since time is inverse of rate, it will take 42/13 = 3 3/13 = 3.23 hours.

_________________

Jeffrey Miller
Head of GMAT Instruction
jeff@targettestprep.com

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