Why take the integral of this instead of just plugging in the number?

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Homework Help Overview

The discussion revolves around a problem involving the rate of oil leaking from a ruptured storage tank, described by the function r(t) = 100 e^(-0.01t) liters per minute. Participants explore the reasoning behind using integration to determine the total amount of oil leaked over the first hour, rather than simply substituting a value into the rate function.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants discuss the necessity of integration due to the non-constant nature of the leakage rate over time. Questions are raised about the implications of directly substituting a time value into the rate function, with some participants reflecting on their understanding of the relationship between rates and integrals.

Discussion Status

There is an ongoing exploration of the reasoning behind the integration process, with some participants affirming the need to integrate to account for the varying rate of leakage. Guidance has been offered regarding the interpretation of the rate as an instantaneous measure, prompting further inquiry into the mathematical principles involved.

Contextual Notes

Some participants note that the problem is situated within a section of their textbook focused on U-Substitution, suggesting a context of learning about integration techniques.

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Homework Statement



An oil storage tank ruptures at time t = 0 and oil leaks from the tank at a rate of r(t) = 100 e^(-0.01t) liters per minute. How much oil leaks out during the first hour?

Homework Equations



r(t) = 100 e^(-0.01t)

The Attempt at a Solution



Eh, I already got the answer, I just did a definite integral from 0 to 60 for the equation.
My question is: Why would you find the integral instead of just plugging in 60 for t into that equation? Is it because that equation is a rate, so it's a derivative and you have to take the integral to get the original equation?
 
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Rate multiplied by Time give the amount of oil leaked, but the rate is not constant. As you guessed, you integrate because the rate changes with time. NOT constant.

Another explanation: What if you just plug in the number?
If you just plug in, what... 60? Then this give you r(60)=100e^(-0.01*60)=54.88 liters per minute. But from time 0 to time 60, the rate was NOT 54.88, so you would be calculating the liters for 60 minutes at the mostly wrong rate of 54.88 liters per minute. This is a very large underestimation. The actual rate is different at every point in time from 0 to 60, and this rate VARIES with time. So,... integrate.
 
Last edited:
Xetman said:

Homework Statement



An oil storage tank ruptures at time t = 0 and oil leaks from the tank at a rate of r(t) = 100 e^(-0.01t) liters per minute. How much oil leaks out during the first hour?

Homework Equations



r(t) = 100 e^(-0.01t)

The Attempt at a Solution



Eh, I already got the answer, I just did a definite integral from 0 to 60 for the equation.
My question is: Why would you find the integral instead of just plugging in 60 for t into that equation? Is it because that equation is a rate, so it's a derivative and you have to take the integral to get the original equation?

Why did you integrate? That was the correct thing to do, but you claim you did it without knowing why. Did somebody tell you to do it, or what?
 
Nah lol the question was in the U-Substitution section of my book so I figured it wouldn't be that easy just to plug in a number.
 
Xetman said:
Is it because that equation is a rate, so it's a derivative and you have to take the integral to get the original equation?

You've kind of answered your own question here. Yes, the expression you're given is a rate (an instantaneous volume per unit time), so you need to integrate with respect to time to get the total volume that leaks out over a time interval. The definite integral just sets the bounds (i.e. answers the question: what's the total volume leaking out from the start [t=0] till t = 60?).
 

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