Growth and decay fomula N(t) = Noe^kt

Question

A 40 gram sample of a substance that's used for drug research has a k-value of 0.1472.

 

Question: Find the substance's half-life,in days. Round your answer to the nearest tenth.

 

 

Growth and decay formula - N(t) = Noe^kt

Answer 1

The decay formula should be:

 

N(t) = N₀e^-kt    note the negative sign

20 = 40e^-0.1472t

0.5 = e^-0.1472t

ln 0.5 = -0.1472t ln e

-0.6931 ≈ -0.1472 t

4.70888 ≈ t

 

The half life is approximately 4.7 days