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The midpoints of the sides of the large square are joined to form a smaller square. what is the area of the smaller square

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

Write an inequality for this description. - one fourth of the opposite of the difference of five and a number is less than twenty.