AP Calculus AB : Definite integral of the rate of change of a quantity over an interval interpreted as the change of the quantity over the interval

Study concepts, example questions & explanations for AP Calculus AB

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Example Questions

Example Question #23 : Interpretations And Properties Of Definite Integrals

A pot of water begins at a temperature of  and is heated at a rate of  degrees Celsius per minute. What will the temperature of the water be after 4 minutes?

Possible Answers:

Correct answer:

Explanation:

Let  denote the temperature of the pot after  minutes.

 

The first thing to realize is that the quantity  is the derivative of . Using the fundamental theorem of Calculus, we know that 

 

From there, we just need to solve the integral. Letting u = t+1, du=dt, we have the following:

Where the second equality follows by the power rule, and re-substituting t+1 = u.

Thus, we now have the equation . Because we know that the water started at , all we need to do is rearrange and substitute.

 

Yielding our final answer, 

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