Complex fraction simplification  TOPIC_SOLVED

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Complex fraction simplification

Postby chillywings on Thu Mar 06, 2014 7:04 pm

Hi, so I'm working through some problems and see two apparently contradicting rules for simplifying a 'fraction over a fraction'. Sorry I cannot figure out how to write proper expressions here... I'm just going to type them out as best as I can.

First, there's x/5 over 2. My solution was to move the 2 up to the top and get 2x/5. Book says no, answer is x/10. Apparently, instead of multiplying by 2/2, I must multiply by 1/2. Ok, this makes sense if you plug in x=1, then .2/2 is .1, not .4. And dividing a number by 5 then also by 2 would be the same as dividing by 10. Damn, don't know where I got that idea from.

Along comes another problem, where we have 1/(x+1)/x. Solution? x/(x+1). Wtf? Thought I couldn't do that? But this makes sense by multiplying by x/x. Now, in the first problem, the 'small fraction' is in the top portion of the 'big fraction'. In the this one, it's in the bottom portion. But last I checked PEMDAS, this shouldn't make a freaking difference

Could someone explain the difference here? I'm clearly missing something...

Thank you
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Re: Complex fraction simplification

Postby stapel_eliz on Thu Mar 06, 2014 9:44 pm

chillywings wrote:First, there's x/5 over 2.

Which of the following do you mean?

. . . . .
. . . . .

chillywings wrote:we have 1/(x+1)/x.

Which of the following do you mean?

. . . . .
. . . . .
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Re: Complex fraction simplification

Postby chillywings on Thu Mar 06, 2014 10:38 pm

b and c. Thanks for the conversion. Do I merely have to operate as though those parenthesis are there all the time?
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Re: Complex fraction simplification  TOPIC_SOLVED

Postby theshadow on Fri Mar 07, 2014 12:03 am

stapel_eliz wrote:. . . . .

. . . . .
chillywings wrote:b and c. Thanks for the conversion. Do I merely have to operate as though those parenthesis are there all the time?

If theres no parentheses then you cant tell what they mean. You have to respect the parens!
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