Combined Rate of Two Machines Welcome! You are encouraged to register with the site and login (for free). When you register, you support the site and your question history is saved.It would take one machine 7 hours to complete a large production order and another machine 5 hours to complete the same order. If they can work on the order simultaneously without interfering with each other, how many hours would it take both machines, working simultaneously at their respective constant rates, to complete the order? Review Answer