SOLUTION: Why the speed of one train with respect to other train is twice when they are running parallel to each other but in opposite directions

Question 1000249: Why the speed of one train with respect to other train is twice when they are running parallel to each other but in opposite directions
Answer by josgarithmetic(39630) (Show Source): You can put this solution on YOUR website!
Opposite direction restricting to one dimension, and usage of signed numbers.

If both trains SPEEDS are each r,

WhichWay
DIRECTION     r
OPPOSITE     -r

These will have their own sizes on a number line, find the difference in RATE (not speed, but rate; now you are dealing with the meaning of direction, not just size alone).

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