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1.11.8 Interpreting solutions of differential equations (A-level only)

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Question 18

A pharmacist is studying the elimination of a medication from the bloodstream. The mass of the medication in the body is modeled by the equation

m=m0e−kt m = m_0 e^{-kt} m=m0​e−kt

where m0m_0m0​ mg is the initial mass administered and mmm mg is the mass in the body after ttt hours.

On average, the biological half-life of this medication is 4.5 hours.

A patient is given a single dose of 300 mg of the medication.

a.

The patient takes the 300 mg dose at 9 am. Use the model to estimate the mass of the medication remaining in the body at 3 pm.

[4]
b.

The patient is instructed to ensure that the total mass of the medication in their body does not exceed 350 mg. The patient intends to take a second 300 mg dose. Using the model, find the earliest time they can take this second dose. Give your answer to the nearest minute.

[4]
c.

State one reason why the mass of medication predicted by this model might not be accurate for an individual patient.

[1]

1.11.8 Interpreting solutions of differential equations (A-level only) Questions

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  3. /1.11.8 Interpreting solutions of differential equations (A-level only)