document.write( "Question 937584: A new automatic machine can do a job in 1 hour less than an older machine. Together they can do the same job in 1.2 hours. How long would it take each machine to do the job alone? \n" ); document.write( "
Algebra.Com's Answer #571024 by TimothyLamb(4379)\"\" \"About 
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x = time for old machine
\n" ); document.write( "y = time for new machine
\n" ); document.write( "---
\n" ); document.write( "y = x - 1
\n" ); document.write( "---
\n" ); document.write( "r = w/t
\n" ); document.write( "rates are additive:
\n" ); document.write( "r = 1/x + 1/y
\n" ); document.write( "t = w/r
\n" ); document.write( "t = 1/(1/x + 1/y)
\n" ); document.write( "1.2 = 1/(1/x + 1/y)
\n" ); document.write( "1.2(1/x + 1/y) = 1
\n" ); document.write( "1.2/x + 1.2/y = 1
\n" ); document.write( "1.2y/xy + 1.2x/xy = 1
\n" ); document.write( "1.2y + 1.2x = xy
\n" ); document.write( "1.2(y + x) = xy
\n" ); document.write( "---
\n" ); document.write( "substitute y = x - 1
\n" ); document.write( "---
\n" ); document.write( "1.2(x - 1 + x) = x(x - 1)
\n" ); document.write( "1.2(2x - 1) = xx - x
\n" ); document.write( "2.4x - 1.2 = xx - x
\n" ); document.write( "xx - x - 2.4x + 1.2 = 0
\n" ); document.write( "xx - 3.4x + 1.2 = 0
\n" ); document.write( "---
\n" ); document.write( "the above quadratic equation is in standard form, with a=1, b=-3.4 and c=1.2
\n" ); document.write( "---
\n" ); document.write( "to solve the quadratic equation, by using the quadratic formula, copy and paste this:
\n" ); document.write( "1 -3.4 1.2
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\n" ); document.write( "---
\n" ); document.write( "the quadratic has two real roots at:
\n" ); document.write( "---
\n" ); document.write( "x = 3
\n" ); document.write( "x = 0.4
\n" ); document.write( "---
\n" ); document.write( "the root x=0.4 makes y negative and doesn't fit the problem statement, so use the root x=3:
\n" ); document.write( "---
\n" ); document.write( "x = 3
\n" ); document.write( "y = x - 1
\n" ); document.write( "y = 2
\n" ); document.write( "---
\n" ); document.write( "answer:
\n" ); document.write( "x = time for old machine = 3 hours
\n" ); document.write( "x = time for new machine = 2 hours
\n" ); document.write( "---
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\n" ); document.write( "Solve and graph linear equations:
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\n" ); document.write( "Solve quadratic equations with quadratic formula:
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