fractuin = fraction

What the reason that multiplication of fractions is:

Suppse:

a/b, c/d are fraction.

The product:

(a / b) * (c / d) = ac / bd

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- Feb 17th 2018, 08:47 AM #1

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- Feb 17th 2018, 01:15 PM #2

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## Re: fractuin

The "reason" is simply that it's the correct way!

Try it yourself...use actual fractions...

Try using google...here's a site:

https://www.mathsisfun.com/fractions...plication.html

- Feb 20th 2018, 08:38 AM #3

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## Re: fractuin

One way to look at this is that the denominators of fractions are "units".

If you have 2/3 you have two of these things we call "thirds"- in the same way that is you have "2 meters" you have two of these things we call "meters". Just as if we have a rectangle with width 3 meters and height 20 cm then the rectangle has area 60 "cm-meters" which we would probably convert to either 6000 cm^2 or 0.6 m^2, that is, we multiply the numbers and multiply the units, so 2 thirds time 5 sevenths is 10 "thirds-sevenths" which we would call 10 "twentyfirsts" or 10/21.

- Mar 7th 2018, 12:32 PM #4

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## Re: fractuin

You can work it out this way ...

a/b * c/d =answer

Multiply both sides by b

a * c/d =b * answer

Multiply both sides by d

a * c = b * d * answer

Divide both sides by a

c = (b * d) / a * answer

Divide both sides by c

1 = (b * d) / (a * c) * answer

Multiply both sides by (a * c)

(a * c) = (b * d) * answer

Divide both sides by (b * d)

(a * c)/(b * d) = answer

or....

answer = (a * c)/(b * d)

Substituting a/b * c/d for answer from a/b * c/d =answer

a/b * c/d = (a * c)/(b * d)

Steve