SOLUTION: A new computer can process a company's monthly payroll in 1 hour less time than the old computer. To really save time, the managert user both computers finished the payroll in 3 ho

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Question 317234: A new computer can process a company's monthly payroll in 1 hour less time than the old computer. To really save time, the managert user both computers finished the payroll in 3 hours. How long would it take the new computer to do the payroll by itself?
Answer by checkley77(12844) About Me  (Show Source):
You can put this solution on YOUR website!
1/(x-1)+1/x=1/3 find the LCM x(x-1).
(x+x-1)/x(x-1)=1/3 combine like terms.
(2x-1)/(x^2-x)=1/3 cross multiply.
x^2-x=3(2x-1)
x^2-x=6x-3
x^2-x-6x+3=0
x^2-7x+3=0
x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+
x=(7+-sqrt[-7^2-4*1*3])/2*1
x=(7+-sqrt[49+12])/2
x=(7+-sqrt37)/2
x=(7+-6.08)/2
x=(7+6.08)/2
x=13.08/2
x=6.54 hrs. for the old machine.
6.54-1=5.54 hrs. for the newer machine.
Proof:
1/5.54+1/6.54=1/3
.181+.153=.333
.334~.333