SOLUTION: Marco can build a laptop twice as fast as Cliff. Working together, it takes them 5 hours. How long would it have taken Marco working alone?

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Question 1080095: Marco can build a laptop twice as fast as Cliff. Working together, it takes them 5 hours. How long would it have taken Marco working alone?
Answer by ikleyn(52799) About Me  (Show Source):
You can put this solution on YOUR website!
.
Let "m" be the Marco's rate of work.

Then Cliff's rate of work is m%2F2, according to the condition.


Also, the condition says that 

m+%2B+m%2F2 = 1%2F5,

which means that %282m%29%2F2+%2Bm%2F2 = 1%2F5,   or   3m%2F2 = 1%2F5,  m = 2%2F%285%2A3%29= 2%2F15.


Hence, It will take 15%2F2 = 7.5 hours for Marko to complete the job working alone.


Answer.  It will take 7 hours and 30 minutes for Marko to complete the job working alone.


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
    - Using quadratic equations to solve word problems on joint work
    - Solving rate of work problem by reducing to a system of linear equations
    - Selected joint-work word problems from the archive
    - Joint-work problems for 3 participants
    - Had there were more workers, the job would be completed sooner
    - One unusual joint work problem


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".