Example

Try It 10.88: Evaluating an Exponential Decay Model

Practice solving an exponential decay problem by determining the decay rate and applying it to find a future amount. Suppose a bacteria population declines from 700,000700{,}000 to 400,000400{,}000 in 55 hours. Using the exponential decay formula A=A0ektA = A_0 e^{kt}, substitute the given values: 400,000=700,000ek5400{,}000 = 700{,}000 e^{k \cdot 5}. Dividing by 700,000700{,}000 gives 47=e5k\frac{4}{7} = e^{5k}. Taking the natural logarithm of both sides results in ln(47)=5k\ln\left(\frac{4}{7}\right) = 5k, so the decay rate is k=ln(4/7)5k = \frac{\ln(4/7)}{5}. To find the population after 2424 hours, use this rate in the formula: A=700,000eln(4/7)524A = 700{,}000 e^{\frac{\ln(4/7)}{5} \cdot 24}. Evaluating this expression yields approximately 47,70047{,}700. Thus, there will be about 47,70047{,}700 bacteria remaining.

0

1

Updated 2026-05-26

Contributors are:

Who are from:

Tags

OpenStax

Intermediate Algebra @ OpenStax

Ch.10 Exponential and Logarithmic Functions - Intermediate Algebra @ OpenStax

Algebra

Learn After