Mathematics: The Law and Order detectives enter a house at 11:30 am and found a man on the floor murdered. They take his body temperature finding to be 91.8 F. The body is taken to the morgue and at 12:30 pm the body temperature is 84.4 F. Using an exponential model for the body temperature, to the nearest minute, what time was he killed. Normal body temperature is 98.6.

The Law and Order detectives enter a house at 11:30

fatty18

22.04.2021

Time of murder = 10:39 am

Step-by-step explanation:

Let the equation of exponential function representing the final temperature of the body after time 't' is,

f(t) = $a(e)^{nt}$

Here, a = Initial temperature

n = Constant for the change in temperature

t = Duration

At 11:30 am temperature of the body was 91.8°F.

91.8 = $98.6(e)^{nt}$ --------(1)

Time to reach the body to the morgue = 12:30 pm

Duration to reach = 12:30 p.m. - 11:30 a.m.

= 1 hour

Therefore, equation will be,

84.4 = $91.8(e)^{n\times 1}$

eⁿ = $\frac{84.4}{91.8}$

ln(eⁿ) = ln(0.9194)

n = -0.08403

From equation (1),

91.8 = $98.6(e)^{-0.08403t}$

$(e)^{0.08403t}=\frac{98.6}{91.8}$

$ln[(e)^{0.08403t}]=ln[\frac{98.6}{91.8}]$

0.08403t = 0.07146

t = 0.85 hours

t ≈ 51 minutes

Therefore, murder was done 51 minutes before the detectives arrival.

Time of murder = 11:30 - 00:51

= 10:90 - 00:51

= 10:39 am

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