Question
The number of milligrams \( D(h) \) of a drug in a patient's bloodstream \( h \) hours after the drug is injected is modeled by the following function. \[ D(h)=30 e^{-0.35 h} \] Find the initial amount injected and the amount in the bloodstream after 7 hours. Round your answers to the nearest hundredth as necessary. Initial amount:
Ask by Grant Kelley. in the United States
Mar 31,2025
Upstudy AI Solution
Tutor-Verified Answer
Answer
The initial amount injected is 30 milligrams, and after 7 hours, there are approximately 2.59 milligrams in the bloodstream.
Solution
We begin with the function
\[
D(h)=30 e^{-0.35h}
\]
which models the number of milligrams of the drug in the bloodstream \( h \) hours after injection.
### Step 1. Find the initial amount injected
The initial amount corresponds to \( h=0 \). Substitute \( h=0 \) into the function:
\[
D(0)=30e^{-0.35(0)}=30e^0=30
\]
Thus, the initial amount injected is \( \boxed{30} \) milligrams.
### Step 2. Find the amount in the bloodstream after 7 hours
Substitute \( h=7 \) into the function:
\[
D(7)=30e^{-0.35(7)}=30e^{-2.45}
\]
Using a calculator, we find:
\[
e^{-2.45} \approx 0.0863
\]
Thus,
\[
D(7) \approx 30 \times 0.0863 \approx 2.59
\]
After 7 hours, the amount in the bloodstream is approximately \( \boxed{2.59} \) milligrams.
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Bonus Knowledge
To find the initial amount injected, we evaluate \( D(0) \): \[ D(0) = 30 e^{-0.35 \cdot 0} = 30 e^{0} = 30 \text{ mg} \] So, the initial amount injected is 30 mg. Next, let's determine the amount in the bloodstream after 7 hours by calculating \( D(7) \): \[ D(7) = 30 e^{-0.35 \cdot 7} = 30 e^{-2.45} \approx 30 \cdot 0.086 = 2.58 \text{ mg} \] After rounding to the nearest hundredth, the amount in the bloodstream after 7 hours is approximately 2.58 mg.