At the moment a certain medicine is injected, its concentration in the bloodstream is

\[120\] milligrams per liter. From that moment forward, the medicine's concentration drops by
\[30\%\] each hour.
Write a function that gives the medicine's concentration in milligrams per liter,
\[C(t)\],
\[t\] hours after the medicine was injected.
\[C(t)=\]

2 answers

To model the concentration of the medicine in the bloodstream over time, we can use the formula for exponential decay. The concentration drops by \(30%\) each hour, which means that \(70%\) of the concentration remains after each hour.

Initially, the concentration \(C(0)\) is \(120\) milligrams per liter. After \(t\) hours, the concentration can be calculated as follows:

\[ C(t) = C(0) \times (1 - r)^t \]

where \(r\) is the decay rate. Given that the concentration drops by \(30%\), we have:

\[ r = 0.30 \]

Thus, \(1 - r = 0.70\). Plugging in the initial concentration:

\[ C(t) = 120 \times (0.70)^t \]

This gives us the function for the concentration of the medicine in the bloodstream \(t\) hours after the injection:

\[ C(t) = 120 \times (0.70)^t \]

This equation will allow you to find the concentration of the medicine at any given hour \(t\) after injection.

V