Solve Word Problem: Find a and b in T(t)=250-ae^(-bt)

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Homework Help Overview

The problem involves a yam placed in an oven at a constant temperature of 250 degrees Celsius. After 30 minutes, the temperature of the yam is recorded at 150 degrees Celsius, with a rate of increase of 3 degrees Celsius per minute. The temperature is modeled by the equation T(t)=250-ae^(-bt), and the task is to find the constants a and b.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the values of T(30) and T'(30) and how these can be utilized to determine a and b. There is a reference to Newton's law of cooling as a potential guiding principle. One participant attempts to derive the value of b using the given temperature conditions and seeks clarification on how to subsequently find a.

Discussion Status

The discussion is active, with participants exploring various approaches to find the constants a and b. Some guidance has been offered regarding the use of temperature values and the application of Newton's law of cooling. There is no explicit consensus yet, as participants are still working through the problem.

Contextual Notes

Participants are navigating the constraints of the problem, including the specific temperature readings and the rate of change provided. There is an emphasis on deriving values from the model without providing complete solutions.

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Homework Statement



A yam is pust in an oven maintained at a constant temp of 250degrees C. Suppose that after 30 min the temp of the yam is 150degrees C and is increasing at a rate of 3degrees C/min. If the temp of the yam t minutes after it is put in the oven is modeled by
T(t)=250-ae^(-bt), find a and b.

Homework Equations





The Attempt at a Solution



I have no idea how to even start. Please help
 
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Just by looking at the question as stated, what are the values of:

T(30)
T'(30) ?

How can you use these to find a and b?
 
betsinda said:
A yam is pust in an oven maintained at a constant temp of 250degrees C. Suppose that after 30 min the temp of the yam is 150degrees C and is increasing at a rate of 3degrees C/min. If the temp of the yam t minutes after it is put in the oven is modeled by
T(t)=250-ae^(-bt), find a and b.

Hi betsinda! :smile:

Hint: what is Newton's law of cooling?
 
I think I have found b

180 = 250 - ae^-40b
150 = 250 - ae^-30b


-70 = -ae^-40b
70/e^-40b = a

-100 = -70/e^-40b * e^-30b
100/70 = e^40b * e ^-30b
10/7 = e^10b
ln 10/7 = 10 b
b = ln(10/7)/10

but how do I find a?
 
betsinda said:
70/e^-40b = a
:
10/7 = e^10b

but how do I find a?

a = 70e40b = 70(e10b)4 :wink:
 
Thank you !
 

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