An element with mass 490 grams decays by 28.6% per minute. How much of the element is remaining after 16 minutes, to the nearest 10th of a gram?

Answer 1

This is an example of exponential decay. At the end of each minute, the remaining percentage is (100-28.6)% = 71.4% of the amount present at the start of the minute, which is 0.714 times the amount at the start of the minute. The relation is

m(t) = m₀ (0.714)^t

t = total elapsed time in minutes

m₀ = 490 g (the amount present at time t = 0)

m(t) = (490 g) (0.714)^t

Now plug in t in minutes and finish from here.