The average length of a rural route is 55 miles.
( ( ( The ( average length ) ) ( of ( a ( rural route ) ) ) ) ( ( is ( 55 miles ) ) . ) )
(ROOT (S (NP (NP (DT The) (JJ average) (NN length)) (PP (IN of) (NP (DT a) (JJ rural) (NN route)))) (VP (VBZ is) (NP (CD 55) (NNS miles))) (. .)))
100 miles is the average for a rural route.
( ( 100 miles ) ( ( is ( ( the average ) ( for ( a ( rural route ) ) ) ) ) . ) )
(ROOT (S (NP (CD 100) (NNS miles)) (VP (VBZ is) (NP (NP (DT the) (NN average)) (PP (IN for) (NP (DT a) (JJ rural) (NN route))))) (. .)))