Bunuel wrote:

Tough and Tricky questions: Work/Rate Problems.

Working individually, Deborah can wash all the dishes from her friend’s wedding banquet in 5 hours and Tom can wash all the dishes in 6 hours. If Deborah and Tom work together but independently at the task for 2 hours, at which point Tom leaves, how many remaining hours will it take Deborah to complete the task alone?

A. 4/15

B. 3/11

C. 4/3

D. 15/11

E. 11/2

Kudos for a correct solution.Source: Chili Hot GMAT

Deborah can complete the job in 5 hrs so one hour work is 1/5

Tom can complete the same job in 6 hrs so one hour work is 1/6

amount of work complete in in one hour by both working together = 1/5+1/6 = 11/30

they both work together for 2 hours , thus work done in 2 hrs = 22/30

work left = 1-(22/30) = 8/30

after 2 hrs tom left and the remaining work will be complete by Deborah

Deborah complete 1 work in 5 hrs, then 8/30 work will be completed in 5*8/30 hrs i.e 4/3

[C]

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