Atoxic radioactive substance with a density of 2 milligrams per square centimeter is detected in the ventilating ducts of a nuclear processing building that was used 45 years ago. if the half- life of the substance is 20 years, what was the density of the substance when it was deposited 45 years ago?

Which of the following individuals' diet is following the usda's dietary guidelines? a. everything peter eats from the grain group is considered refined grains. b. kim likes carrots, so that is the only vegetable she eats. c. craig consumes nutrient-dense foods. d. brook eats mostly fast foods and sweets.