median
don steward
mathematics teaching 10 ~ 16

Tuesday, 4 June 2013

multiplying directed numbers

using a grid can establish some rationale for the multiplication of two negative numbers being a positive number

this approach was suggested to me by Gill Hatch, when she was at Manchester Metropolitan University

a powerpoint goes through the solution steps
but it's probably better developed with student suggestions

firstly, using some examples of 5 (down) times 6 (across)
establish that the answer must be 30

eventually there may be a suggestion that involves two negatives (as in the 4th one)

knowing that the overall total must be 30 identifies the bottom right hand product needed to make this total



No comments: