developing strategies for addition + Subtraction

the most appropriate method of computation

is important for math literacy

use of manipulatives or drawings 

not the standard algorithm or counting

vs. standard algorithms

number oriented rather than digit oriented

left-handed rather than right-handed

flexible vs. "one right way"

student-invented strategies

COMPUTATION + estimation

part of "doing mathematics"

"let's understand why this works!"

are not spontaneously invented

for inventing strategies