Question 7
Tom has a contract to dig out some foundations, and it must be done in 30 days. His own machine, which he wishes to use as much as possible, would take 48 days to do all the work. He can hire a bigger machine which would do the complete job in 21 days, but it costs 300 dollars a day. There is only enough room for one machine at a time. What is the least number of days for which he will have to hire the larger machine?