Two approaches to subtraction practice:
I. A 2nd grade Investigations sheet, from mid-way through the 2nd grade curriculum, Putting Together and Taking Apart, p. 135 [click to enlarge]:
II. A subtraction exercise from early on in the 2nd grade Singapore Math Curriculum, Primary Mathematics 2A, p. 35 [click to enlarge]:
III. Extra Credit:
1. Map the assignment to the teaching protocol:
a. Telling you which strategy to use
b. Providing feedback about whether your answer is correct
2. Which assignment is more Constructivist?