Question

Strontium 90 is a radioactive isotope that decays according to the eqaution A t = A 0 e − 0.0244 t , where A 0 is the initial amount present and A t is the amount present after t years. If you begin with 400 grams of strontium 90,

(a) How much strontium 90 will be left after 10 years? Round your answer to the nearest tenth of a gram. grams
(b) When will 105 grams of strontium 90 be left? Round your answer to the nearest tenth of a year. years
HELP!!!!!!

Answer 1

Explanation:

t = A 0 e − 0.0244 t

t=10 yrs

Ao=400 gm

At= 400 e^-.0244(10) = 313.4 gm

At = 105 = 400e^-.0244t solve for t

105/400 = e^-.0244t

ln (105/400) = -.0244 t

t = 54.8 years