Math Problem Statement

Suppose that a cup of coffee begins at 172◦ F and after sitting in room temperature of 66◦ F for 14 minutes, the coffee reaches 165◦ F.

The differential equation is T(t) = 106e^(1/14ln(99/106)t+66

How long will it take before the coffee reaches 154 degrees? Include at least 2 decimal places in your answer.

? minutes

Solution

To solve this problem, let's work with the given differential equation:

T(t)=106e(114ln(99106))t+66T(t) = 106e^{\left(\frac{1}{14} \ln \left(\frac{99}{106}\right)\right)t} + 66

where:

  • T(t)T(t) is the temperature of the coffee at time tt,
  • T(0)=172FT(0) = 172^\circ F,
  • the coffee cools to 165F165^\circ F after 1414 minutes in a room temperature of 66F66^\circ F,
  • and we want to find the time tt when the coffee temperature T(t)T(t) reaches 154F154^\circ F.

Step-by-Step Solution

  1. Set up the equation for T(t)=154T(t) = 154: 154=106e(114ln(99106))t+66154 = 106e^{\left(\frac{1}{14} \ln \left(\frac{99}{106}\right)\right)t} + 66

  2. Isolate the exponential term: 15466=106e(114ln(99106))t154 - 66 = 106e^{\left(\frac{1}{14} \ln \left(\frac{99}{106}\right)\right)t} 88=106e(114ln(99106))t88 = 106e^{\left(\frac{1}{14} \ln \left(\frac{99}{106}\right)\right)t}

  3. Divide by 106: 88106=e(114ln(99106))t\frac{88}{106} = e^{\left(\frac{1}{14} \ln \left(\frac{99}{106}\right)\right)t}

  4. Take the natural logarithm of both sides to solve for tt: ln(88106)=(114ln(99106))t\ln \left(\frac{88}{106}\right) = \left(\frac{1}{14} \ln \left(\frac{99}{106}\right)\right)t

  5. Isolate tt: t=ln(88106)114ln(99106)t = \frac{\ln \left(\frac{88}{106}\right)}{\frac{1}{14} \ln \left(\frac{99}{106}\right)}

  6. Calculate tt:

    • First, find ln(88106)\ln \left(\frac{88}{106}\right).
    • Then, find ln(99106)\ln \left(\frac{99}{106}\right).
    • Divide these results to get tt.

After performing the calculations, you will get:

t33.62 minutest \approx 33.62 \text{ minutes}

So, it will take approximately 33.62 minutes for the coffee to cool to 154F154^\circ F.

Would you like more details or have any questions?


Related Questions:

  1. How does the room temperature affect the cooling rate of the coffee?
  2. How would the solution change if the initial temperature of the coffee was different?
  3. How does Newton's Law of Cooling apply to this problem?
  4. What would be the temperature of the coffee after 45 minutes?
  5. If the room temperature increased, how would that affect the time to reach 154 degrees?

Tip:

When dealing with exponential decay or growth problems, carefully isolate the variable using logarithmic properties.

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Exponential Decay
Logarithmic Functions
Differential Equations
Newton's Law of Cooling

Formulas

T(t) = 106e^(1/14 * ln(99/106) * t) + 66
t = ln(88/106) / (1/14 * ln(99/106))

Theorems

Newton's Law of Cooling

Suitable Grade Level

Grades 11-12