ROGER F. answered 06/30/15
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DR ROGER - TUTOR OF MATH, PHYSICS AND CHEMISTRY
S = rΘ
7 = 2.25Θ, Θ = 7/2.25 = 3.1 rad
30O = 30O*Π/180O
= Π/6 rad
r = S/Θ = 200/ Π/6 = 1200/Π = 382 cm