Question

Element X is a radioactive isotope such that every 86 years, its mass decreases by half. Given that the initial mass of a sample of Element X is 730 grams, how much of the element would remain after 9 years, to the nearest whole number?

Answer 1

The half-life is 86 years, so the decay function is
730 * (1/2)^(t/86)
So plug in t=9

Answer 2

Answer is 679
730 * (1/2)^(9/86)
=679