Exponential decay problem

thewizard

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I'm having trouble with this question, I was wondering if anyone could lend a hand. I got an answer but it doesn't seem right as the timings don't add up.

The police discover a murder victim at 5:15 a.m. They measure the body temperature of the victim and record it as 30°C. Hercule Marple arrives on the scene of the crime 30 minutes later and measures the body temperature again. He records it as 27°C. The temperature of the room is recorded as 15°C and assumed to be constant. Hercule Marple, knowing that normal body temperature is 37°C, wants to estimate the time of death of the victim.

If the cooling process is modelled by the equation q = q0e−kt , where q is the excess temperature (body temperature minus room temperature), and q0 and k are constants, estimate the time of death.

(ii) When Miss Poirot arrives and investigates closely, she finds that the police and Hercule have been sloppy recording the figures. The real measurements should have been 29.6°C at 5:14am and 27.4°C at 5:46am, and the room temperature was really 14.6°C. How far out is the original estimate of the time of death?
 
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I'm having trouble with this question, I was wondering if anyone could lend a hand. I got an answer but it doesn't seem right as the timings don't add up.

The police discover a murder victim at 5:15 a.m. They measure the body temperature of the victim and record it as 30°C. Hercule Marple arrives on the scene of the crime 30 minutes later and measures the body temperature again. He records it as 27°C. The temperature of the room is recorded as 15°C and assumed to be constant. Hercule Marple, knowing that normal body temperature is 37°C, wants to estimate the time of death of the victim.

If the cooling process is modelled by the equation q = q0e−kt , where q is the excess temperature (body temperature minus room temperature), and q0 and k are constants, estimate the time of death.

(ii) When Miss Poirot arrives and investigates closely, she finds that the police and Hercule have been sloppy recording the figures. The real measurements should have been 29.6°C at 5:14am and 27.4°C at 5:46am, and the room temperature was really 14.6°C. How far out is the original estimate of the time of death?

What are your thoughts?

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