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?

Life expectancy in the united states is (76.4 for men and 81.1 for women). life expectancy is not the same as healthy life expectancy. healthy life expectancy is the number of years a person is expected to live in this number is obtained by subtracting years spent in poor health from overall life expectancy. the world health organization (who) calculates healthy life expectancy in 194 countries. the united states ranks twenty-ninth in the world using this measurement, with an average of of healthy life expectancy. singapore ranks number one (76 years), and japan is number two (75 years).