Can I say "arm reach is" instead of "arm reach of"?
Native speaker’s answer
Rebecca
No, it would sound unnatural to say "an arm reach is" instead of "an arm reach of" in this case. "Arm" in "arm reach" acts as an adjective to describe the action of reaching out one's arm. The preposition "of" sounds the most natural to use after "arm reach" because it gives a specific value after an action of 7 feet.