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When i add money am i supposed to make it like this 7+12 or 7.00+12.00 because i got 19 dollars for my answer

Apinhole camera is made out of a light-tight box with a piece of film attached to one side and pinhole on the opposite side. the optimum diameter d(in millimeters) of the pinhole can be modeled by d=1.9[ (5.5 x 10^-4) l) ] ^1/2, where l is the length of the camera box (in millimeters). what is the optimum diameter for a pinhole camera if the camera box has a length of 10 centimeters

Using inductive reasoning, what are the next two number in this set? 2,3/2,4/3,5/4,