A scientist begins with 100 mg of a radioactive substance. After 6 days, it has decayed to 60 mg. How long after the process began will it take to decay to 10 mg?
For radioactive decay: N = N(0) x exp(-λt) ln(6/10) = -6λ λ = 0.085 For the amount to become 10mg: 10 = 100exp(-0.085t) (ln(1/10)) / -0.085 = t t = 27.1 days
