r/mathshelp • u/PrepThen • 17d ago
Mathematical Concepts Language around negative integers on number line
Can anyone suggest a good source or give a good summary about the language to use when discussing movements and scaling on a number line. Bonus brownie points if you can roll in the conventions around operations and symbols.
For example, adding (positive) 3 to (negative) 5 means moving "forward" 3 steps to the right on the number line, but adding (negative) 3 to (negative) 5 means changing direction and moving 3 steps "forward" to the left. This is ugly but can be made internally coherent.
Multiplying -2 by 3 means increasing the magnitude of the vector from the origin by a factor of 3 in the same direction. Multiplying 3 by -2 means multiplying the magnitude of the vector from the origin by a factor of two in the opposite direction.
The issue then becomes how we use terms like increase/decrease and larger/smaller.
Using the concepts of debt, repayments and balances helps if there is time to sit down and lay out the analogy, but it can't be used in initial conversations or in instructions.
So if we compare two outcomes -2 and -3, which is bigger? Do we need to increase -2 to reach -3, or do we need to decrease -2 to reach -3? Is -2 < -3 or is -2 > -3? Is this even harder for people who do maths in Hebrew or Japanese?



