Subtract three-digit numbers that require one regrouping using the standard algorithm. The first problems include a disk model to illustrate the subtraction and the regrouping. The remaining problems do not use a disk model
B. Solve 3-digit column subtraction with multiple exchanges
C. Model 2-step exchanges in subtraction problems using a disk model
D. Solve 3-digit column subtraction with 2-step exchanges with and without using a disk model
E. Solve 3-digit column subtraction with 2-step exchanges