SOLUTION: two old machines and a new one are put to work on a contract. Each of the old ones requires twice as much time as the new one to do the job. Together, the three machines complete t

Question 697146: two old machines and a new one are put to work on a contract. Each of the old ones requires twice as much time as the new one to do the job. Together, the three machines complete the work in 2 days. How long would it take each machine to do the work alone?
Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website!
Add their rates of working to get their
rate working together
Let = the rate for an old machine
Let = the rate for a new machine
(1)
Note that twice the time means half the rate
----------
Given: 3 machines working together have
a rate of ( 1 contract ) / ( 2 days )
(2)
(2)
Substitute (1) into (2)
(2)
(2)
(2)
(2)
and, since
(1)
(1)
(1)
Each old machine takes 8 days to do the work alone
Each new machine takes 4 days to do the work alone
check:
(2)
(2)
(2)
(2)
OK

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