directed number addition and subtraction 1 (of 2)

the powerpoint is here

uses directed numbers as vectors
involving the start and end (like stations) and the journey
these journeys can be described in two different (but the same) ways

Simon Razvi, in Birmingham (England) suggested that the positions on a number line are like nouns (e.g. 'negative 4')
and the journeys are like verbs (e.g. 'subtract 4')
usually these get muddled up
and usually I think there's value in muddling them up
[technically I guess you can't add a position on a number line to anything!]
it seems to me that it's (one dimensional) vectors that can be added and subtracted

thanks to Worcester Uni (PGCE) students and Jane Moreton for their comments (in Jan 2018)