Adding fractions with a decimal number denominator
- Thread starter Morne
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D
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Yes I can, I'm just struggling with the following question:
1/x = 1/5 + 1/10.68
Thanks for the correction. I've tried it that way now, but still not the result I need
Look at
1/x = 1/2 + 1/3
First clear the number fractions [multiply through by 2 and 3]
6/x = 3 + 2 = 5
Now clear the x fraction
6 = 5 x
Solve
x = 6/5 = 1.2
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But it's not as easy to find the LCM of 5 and 10,68
Well, why wouldn't it be just as easy? It's still the same process, the numbers just look more intimidating is all. For example, to add two fractions with decimal denominators:
\(\displaystyle \frac{6}{12.34}+\frac{1}{56.78}\)
Let's find a common multiple of 12.34 and 56.78. In general, the smaller the better, but when dealing with "weird" numbers, it's sometimes best to settle for any multiple. So we'll use 12.34 * 56.78 = 700.6652 as our denominator:
\(\displaystyle \displaystyle \frac{6}{12.34}+\frac{1}{56.78}=\frac{6\cdot 56.78}{12.34\cdot 56.78}+\frac{1\cdot 12.34}{56.78\cdot 12.34}=\frac{340.68}{700.6652}+\frac{12.34}{700.6652}\)
Now the fractions have a common denominator, so we can add across:
\(\displaystyle \frac{340.68}{700.6652} +\frac{12.34}{700.6652}=\frac{353.02}{700.6652}\)
This is technically a valid answer, although your teacher may prefer either whole number numerators and denominators (in which case you could multiply by 1000 to clear the decimals), or prefer a decimal approximation (in which case you would use a calculator). I'd go with whatever instructions you've been given.
I finally got it right. Thanks very much for your help!!
pka
Elite Member
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- Jan 29, 2005
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For the life-of-me I do not see why one would not simplify his life:
\(\displaystyle \Large\frac{600}{1234}+\frac{100}{5678}\) Ain't any decimals left.
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You don't have to find a LCM, just multiply through by 5, then multiply through by 10,68 then multiply through by x