Why Do We Use the Reciprocal in Fraction Division?

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Discussion Overview

The discussion revolves around the reasoning behind using the reciprocal in the division of fractions. Participants seek to understand the underlying principles and proofs, particularly in the context of algebra.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification

Main Points Raised

  • One participant requests a proof for why the reciprocal is used in fraction division, expressing a desire to understand the reasoning behind the method rather than just the procedure.
  • Another participant asserts that the concept is more of a definition than a proof, explaining that division is the inverse of multiplication, which leads to the conclusion that dividing by a fraction equates to multiplying by its reciprocal.
  • A third participant provides a mathematical representation using LaTeX to illustrate the process of dividing fractions and demonstrates how it leads to the multiplication by the reciprocal.
  • A later reply expresses gratitude for the provided explanation, indicating that it clarified the concept for them.

Areas of Agreement / Disagreement

Participants present differing views on whether the use of the reciprocal in fraction division is a proof or a definition, indicating a lack of consensus on this aspect.

Contextual Notes

The discussion does not resolve the deeper philosophical question of "why" the reciprocal is used, focusing instead on the operational definitions and mathematical representations.

Taylor_1989
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Could someone show me the proof to why we use the reciprocal in fractions division. I ask this because it seem we are taught the how in math but never the why. Algebra proof would be best thanks.
 
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It's not a proof, it's a definition. Division is the inverse operation of multiplication, and so dividing by a fraction is the same as multiplying by the inverse of that fraction, which is its reciprocal.
 
My LaTeX always looks so ugly.

[tex]n = \frac{(\frac{a}{b})}{(\frac{c}{d})}[/tex]
[tex]n\left(\frac{c}{d}\right) = \frac{a}{b}[/tex]
[tex]nc = \frac{ad}{b}[/tex]
[tex]n = \frac{ad}{bc} = \left(\frac{a}{b}\right) \times \left(\frac{d}{c}\right)[/tex]
 
Thanks for the proof abacus, well appreciated makes things clearer for me.
 

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