SOLUTION: There is a series of project activities to be performed by two staff members, Mr. X and Mr. Y. When each of them works alone, it can be completed by Mr. X in 3 hours and by Mr. Y

Question 1088782: There is a series of project activities to be performed by two staff members, Mr. X and Mr. Y. When each of them works alone, it can be completed by Mr. X in 3 hours and by Mr. Y in 6 hours. When Mr. X starts to work at 9:00 a.m. and then Mr. Y starts to work with Mr. X at 10:00 a.m., which of the following is the time at which all the activities are completed? Here, the activities can be divided and performed in parallel by the two members without any loss of productivity.

Answer by ikleyn(52874) (Show Source): You can put this solution on YOUR website!
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From 9:00 am to 10:00 am, Mr.X will complete  of the activity, so  will remain uncompleted.


The rate of work for X is  of the job per hour.


The rate of work for Y is  of the job per hour.


So, their combined rate of work is {{1/3+1/6}}} =  =  =  of the job per hour.


Thus they need  =  =  hours = 1 hour and 20 minutes to complete the job.


So, Mr.X and Mr.Y  will complete their activity 1 hour and 20 minutes after 10:00 am, i.e. at 11:20 am.

Solved.

It is a typical joint work problem.

There is a wide variety of similar solved joint-work problems with detailed explanations in this site. See the lessons
    - Using Fractions to solve word problems on joint work
    - Solving more complicated word problems on joint work
    - Selected joint-work word problems from the archive

Read them and get be trained in solving joint-work problems.

Also, you have this free of charge online textbook in ALGEBRA-I in this site
    - ALGEBRA-I - YOUR ONLINE TEXTBOOK.

The referred lessons are the part of this textbook under the topic
"Rate of work and joint work problems" of the section "Word problems".

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