Half a croissant, on a plate, with a sign in front of it saying '50c'
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Mark Set Go

Something from Nothing leaves Something
  (+7, -1)
(+7, -1)
  [vote for,

I haven't actually had to subtract negatives since about the fifth grade. But, I bet a bunch of teachers have a heck of a time getting everyone's brain wrapped around equations like:


Maybe it's because some of the tricks they're taught to use for such odd problems aren't very consistent with the simple conventions they've learned up to that point. It would suck if some kids were turned off of math right then and there, when no one could offer a consistent rule for subtracting anything from anything.

So, I think a simple routine that works for all +/- operations might help some teachers, while it may also give kids an earlier concept of vectors. Here it is:

1. MARK: Mark the spot of the first number, on a numberline. (eg. -5)

2. SET: Set the direction you will go from that MARK. (eg."-" means point left, toward the negative side of the numberline)

3. GO: Go as many spaces (integers) as the second number, and there's your answer. A negative number just means go opposite the direction you had SET. (eg. -2 means move two spaces in the direction opposite from the left)

This simple mnemonic device is easy to remember, and it keeps operations and values distinct.

Try it. You'll like it. If it works for you, then please, subtract a minus on me. This is my first post.

SwampGas, Apr 14 2010


       Welcome to the halfbakery, a place were the bread wears a smile, and the fish are always hungry. Have a bite at this croissant. My mind is too lazy to work its way round your idea first thing in the morning. I'll leave that to the numerically adept who will inevitably surface.
xenzag, Apr 14 2010

       I always remembered "Two wrongs make a right". If you have two "-" signs, put them together to form a "+" sign.   

       So "-5 - -2" is the same as "-5 + 2".
phundug, Apr 14 2010

       I'm wondering whether children would benefit from beginning each expression with 0. For example,
-5 + 3 is written as "0 - 5 + 3".

       That way you never have to deal with negative numbers, only directional indicators (- means left, + means right; -- you put the two -'s together to form a +).   

       Incidentally, 5 + 3 would be written as 05 + 3, again this does not change the meaning.
phundug, Apr 15 2010

       If you are allowed to write 2 minus signs why not more? 5---3=2 and 2+-+-+2=4   

       However 1-----------------------1=0 true or false?
pocmloc, Apr 15 2010

       Uh, I think that would be absolute zero.^)   

       Interestingly poignant use of the 23 negatives.
SwampGas, Apr 15 2010

       //a place where the bread wears a smile, and the fish are always hungry//   

       That is totally [marked-for-tagline].
wagster, Apr 15 2010

       A more graphical way of doing maths would certainly suit me. However, by the time the maths gets harder, you're doing more advanced maths to draw up the parameters. Though i always imagine the sizes and shapes to understand the concepts (i'm reading a maths book at the moment).
nicholaswhitworth, Apr 15 2010

       Never understood why British English doesn't respect the collective plural form 'math.'
RayfordSteele, Apr 16 2010

       You know the British...always trying to make words difficult to spell/enunciate.
SwampGas, Apr 16 2010

       // words difficult to spell/enunciate //   

       Only if you originate somewhere they are obliged to teach English As A Foreign Language, i.e. North America.
8th of 7, Apr 16 2010


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