document.write( "Question 1142603: Two college students have started their own business building computers from kits. Working alone, one student can build a computer in 20 hours. When the second student helps, they can build a computer in 7.5 hours. How long would it take the second student, working alone to build the computer? create and equation and solve \n" ); document.write( "

Algebra.Com's Answer #763299 by greenestamps(13219) $\"\"$ $\"About$

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\n" ); document.write( "The other tutor has provided a good response showing the traditional algebraic method for solving this kind of \"working together\" problem.

\n" ); document.write( "The problem as posed appears to require an algebraic solution. However, when a problem like this does not require an algebraic solution, here is an alternative method you can use that I find many students like better.

\n" ); document.write( "(1) Consider a common multiple of the two given times.

\n" ); document.write( "(2) The LCM of 7.5 and 20 is 60. 7.5*8 = 60; 20*3 = 60.

\n" ); document.write( "(3) In 60 hours, the one student alone can build 3 of the computers; in 60 hours the two of them together can build 8 of them.

\n" ); document.write( "(4) So the other student can build 5 of the computers in 60 hours; that means he can build 1 computer in 60/5 = 12 hours. \n" ); document.write( "

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