( ( A ( 1 ( MeV gamma-ray ) ) ) ( ( can ( travel ( ( an average ) ( of ( ( 130 meters ) ( in air ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT A) (CD 1) (NN MeV) (NN gamma-ray)) (VP (MD can) (VP (VB travel) (NP (NP (DT an) (NN average)) (PP (IN of) (NP (NP (CD 130) (NNS meters)) (PP (IN in) (NP (NN air)))))))) (. .)))
A 1 MeV gamma-ray can travel an average of 130 meters in air.
(ROOT (S (NP (JJ Meter) (JJ much) (NN distance)) (VP (MD can) (VP (VB beta) (NP (JJ particles) (NN travel)) (PP (IN through) (NP (NN air))))) (. .)))