organizational structure a key enabler of the republic way operating model is our organizational structure that fosters a high performance culture by maintaining 360-degree accountability and full profit and loss responsibility with local 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 .our senior management evaluates , oversees and manages the financial performance of our operations through two field groups , referred to as group 1 and group 2 .group 1 primarily consists of geographic areas located in the western united states , and group 2 primarily consists of geographic areas located in the southeastern and mid-western united states , and the eastern seaboard of the united states .each field group is organized into several areas and each area contains multiple business units or operating locations .each of our field groups and all of our areas provide collection , transfer , recycling and landfill services .see note 14 , segment reporting , to our consolidated financial statements in item 8 of this form 10-k for further discussion of our operating segments .through this operating model , we have rolled out several productivity and cost control initiatives designed to deliver the best service possible to our customers in an efficient and environmentally sound way .fleet automation approximately 75% ( 75 % ) 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 20% ( 20 % ) of our fleet operates on natural gas .we expect to continue our gradual fleet conversion to cng as part of our ordinary annual fleet replacement process .we believe a gradual fleet conversion is the most prudent approach to realizing the full value of our previous fleet investments .approximately 13% ( 13 % ) of our replacement vehicle purchases during 2018 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 capital costs are higher , using cng reduces our overall fleet operating costs through lower fuel expenses .as of december 31 , 2018 , we operated 37 cng fueling stations .standardized maintenance based on an industry trade publication , we operate the seventh largest vocational fleet in the united states .as of december 31 , 2018 , 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', '7000', '7.5'], ['small-container', '4700', '7.0'], ['large-container', '4300', '8.8'], ['total', '16000', '7.7']]
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: what is the ratio of the number of vehicles for the residential line of business to large-container
Answer: 1.63
Explanation: the ratio of the number of cars for the residential line of business to large-container is 1.63 to 1