we realize synergies from consolidating businesses into our existing operations , whether through acquisitions or public-private partnerships , which allow us to reduce capital and expense requirements associated with truck routing , personnel , fleet maintenance , inventories and back-office administration .operating model the goal of our operating model pillar is to deliver a consistent , high quality service to all of our customers through the republic way : one way .everywhere .every day .this approach of developing standardized processes with rigorous controls and tracking allows us to leverage our scale and deliver durable operational excellence .the republic way is the key to harnessing the best of what we do as operators and translating that across all facets of our business .a key enabler of the republic way is our organizational structure that fosters a high performance culture by maintaining 360 degree accountability and full profit and loss responsibility with general management , supported by a functional structure to provide subject matter expertise .this structure allows us to take advantage of our scale by coordinating functionally across all of our markets , while empowering local management to respond to unique market dynamics .we have rolled out several productivity and cost control initiatives designed to deliver the best service possible to our customers in the most efficient and environmentally sound way .fleet automation approximately 72% ( 72 % ) of our residential routes have been converted to automated single driver trucks .by converting our residential routes to automated service , we reduce labor costs , improve driver productivity , decrease emissions and create a safer work environment for our employees .additionally , communities using automated vehicles have higher participation rates in recycling programs , thereby complementing our initiative to expand our recycling capabilities .fleet conversion to compressed natural gas ( cng ) approximately 16% ( 16 % ) of our fleet operates on cng .we expect to continue our gradual fleet conversion to cng , our preferred alternative fuel technology , as part of our ordinary annual fleet replacement process .we believe a gradual fleet conversion is most prudent to realize the full value of our previous fleet investments .approximately 33% ( 33 % ) of our replacement vehicle purchases during 2015 were cng vehicles .we believe using cng vehicles provides us a competitive advantage in communities with strict clean emission initiatives that focus on protecting the environment .although upfront costs are higher , using cng reduces our overall fleet operating costs through lower fuel expenses .as of december 31 , 2015 , we operated 38 cng fueling stations .standardized maintenance based on an industry trade publication , we operate the ninth largest vocational fleet in the united states .as of december 31 , 2015 , our average fleet age in years , by line of business , was as follows : approximate number of vehicles approximate average age .
[['', 'approximate number of vehicles', 'approximate average age'], ['residential', '7200', '7'], ['small-container commercial', '4400', '7'], ['large-container industrial', '4000', '9'], ['total', '15600', '7.5']]
onefleet , our standardized vehicle maintenance program , enables us to use best practices for fleet management , truck care and maintenance .through standardization of core functions , we believe we can minimize variability .

Question: as of december 31 , 2015 what was the ratio of vehicles for the residential to the large-container industrial
Answer: 1.8
Explanation: there are 1.8 residential vehicles for each large-container industrial