is a radioactive material that decays according to the function A t Age scientist has a sample of 800 grams of strontium 90 a What is the decay rate of strontium 90 b How much strontium 90 is left after 20 years c When will only 200 grams of strontium 90 be left d What is the half life of strontium 90 a The decay rate of strontium 90 is 2 44 Type an integer or a decimal Include the negative sign for the decay rate b Approximately 491 grams of strontium 90 is left after 20 years Do not round until the final answer Then round to the nearest whole number as needed c Only 200 grams of strontium 90 will be left in about 56 8 years Do not round until the final answer Then round to the nearest tenth as needed 0 0244t d The half life of strontium 90 is approximately years Do not round until the final answer Then round to the nearest tenth as needed 1 Points 0 5 of 1 15 points where Ao is the initial amount present and A is the amount present at time t in years Assum