Multiply by the Reciprocal, or the LCM?

John Whitaker

Junior Member
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May 9, 2006
Messages
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Is there something in the way the problem is expressed (displayed) that can tip me off to the proper (initial) multiplication procedure... multiply by the Reciprocal, or by the LCM? Thank you.
John Whitaker
 
John Whitaker said:
Is there something in the way the problem is expressed (displayed) that can tip me off to the proper (initial) multiplication procedure... multiply by the Reciprocal, or by the LCM? Thank you.
John Whitaker

It would probably help us to understand your question if you had posted some examples of problems you're puzzled about.

But, that said, I would suggest that if you are given an equation, it is probably a good idea to multiply both sides by the LCD of the denominators of the fractions IN the equation. This should always result in an equation with no fractions.
 
John Whitaker said:
Thanks.

4 - 3x / 7 = 2 + 5x - x/14

is one, and

3/8 = -5/4x

Easier if you rearrange; then lcm process is less painful:
x/14 - 3x/7 = 5x - 2

On your 2nd one: is that (-5/4) times x or -5 divided by 4x?
 
Denis, Thanks. It's 3X = -5/4X or 3d = -5/4d

I haven't forgotten your (a-n)(b-n)(c-n)... (z-n)

I'm not yet smart enough to respond to it.
John
 
John Whitaker said:
Denis, Thanks. It's 3X = -5/4X or 3d = -5/4d

I haven't forgotten your (a-n)(b-n)(c-n)... (z-n)

I'm not yet smart enough to respond to it.
John
Your equation still not clear; why a "X" (or "d") on each side now?
And you're still not clarifying the right side with brackets:
it's either -5/(4X) or (-5/4)X : there's a big difference!

On the puzzle: it's more or less a trick question.....what happens
when the letter on left is n ? :lol:
 
Denis,
I put the "d" in there so you wouldn't confuse x with a multiplication sign. So, using "d" instead of the original "x", I'll restate the problem:

3/8 = -5/4d. Three-eighths equals minus (5 divided by 4) times d.

Is there anything in the way the problem is presented that will clue me as to whether to multiply by the LCD, or by the reciprocal? Thanks.
 
Don't know what you mean with "multiplying by the reciprocal".

"3/8 = -5/4d. Three-eighths equals minus (5 divided by 4) times d."

minus (5 divided by 4) times d = -5d / 4

so 3 / 8 = -5d / 4

I'd crisscross multiply (hate lcd's!):
-40d = 12
-10d = 3
d = -3/10
 
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