How is this simplification possible?

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Discussion Overview

The discussion revolves around the behavior of a mathematical function representing the amount of salt in a tank over time, specifically examining the simplification of the function at large time values. Participants explore the implications of very small numbers in the context of significant figures and numerical representation.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant notes that the function x(t) approaches an asymptotic value of 1 as time increases, despite starting at a much larger value.
  • Another participant explains that adding a very small number to one results in a value that can be approximated as one, highlighting the rapid decrease of the function.
  • Concerns are raised about numerical precision, with one participant mentioning that computers may round very small numbers, affecting calculations.
  • A participant provides an example of the function's value at t=2, indicating that it is very close to 1, suggesting that typical experimental precision may not capture the difference.
  • One participant clarifies that the function does not "simplify to 1" but is approximately equal to 1, depending on the context.

Areas of Agreement / Disagreement

Participants express differing views on the nature of the simplification, with some agreeing that the function can be treated as 1 in practical terms, while others emphasize the distinction between approximation and exact equality.

Contextual Notes

Participants discuss the limitations of numerical precision and significant figures, noting that very small values may not be relevant in practical applications.

Who May Find This Useful

This discussion may be useful for individuals interested in mathematical modeling, numerical analysis, and the implications of significant figures in experimental physics or engineering contexts.

mthoma10
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x(t) = (148/3)e^(-6t) + 1

I am trying to find the amount of salt (x) in the tank at time = 40.

Out of interest I checked it out on wolframalpha, and
(148/3)e^(-240) is around 2.67E(-103) SO RIDICULOUSLY SMALL
but as soon as put the 'plus 1' on the end, it someone all simplifies down to 1?
How is that possible...? thanks!
 
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One plus a very small number is one. The function starts out at ~50 at t=0 and decreases very rapidly to an asympotic value of 1.
 
In addition, computers typically can't handle numbers with that many digits. Rounding has to occur unless you are using a special math library with provision for very long numbers.

Fred
 
To put this into perspective, x(2) = 1.003...
Which means that unless you go to 4 significant figures or more, you won't see a difference.
And most experiments in a lab is only 3 significant figures.

As you have shown, (148/3)e^(-240) only differs from zero in the 102nd decimal place.
You need to think about why you would ever need precision to that level.
 
Strictly speaking, it does NOT "simplify to 1". It is approximately equal to 1 and, depending on the situation can be treated as 1.
 

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