Question

consider the following scenario: a sample of radioactive material has a decay constant of 0.02 per day. if there are initially 20 grams of the material, what formula would you use to determine how much will remain after 10 days?

Answer 1

Use the exponential decay law:
N(t) = N0 e^{-λ t}.

Here N0 = 20 g, λ = 0.02 day⁻¹, t = 10 days, so
N(10) = 20 e^{-0.02·10} = 20 e^{-0.2} ≈ 16.37 grams.