Add four-digit numbers by setting up the problem as column addition and then using disks in a place value chart to visualize the addition. None of the problems require regrouping
A. Add two 4-digit numbers with and without regrouping in one place using a disk model
C. Add two 4-digit numbers with and without regrouping in one place using a disk model part II
D. Add multi-digit numbers with regrouping in multiple places using column addition and disk models
E. Add multi-digit numbers with regrouping in multiple places using column addition
F. Add multi-digit numbers using the standard algorithm