ABSTRACT
When students first learn about subtraction, they learn to subtract each digit of the subtrahend from its counterpart in the minuend: 75-12_ 63. To compute this, they simply subtract 2 from 5 and 1 from 7. Subtraction, with or without regrouping, is a very early topic anyway. Moreover, in using the concept of decomposing a higher value unit, the subtraction procedure is explained in a way that shows its connection with the operation of addition. It not only provides more conceptual support for the learning of subtraction, but reinforces students’ previous learning. Most of the Chinese teachers mentioned the issue of “subtraction within 20” as the conceptual, as well as procedural, “foundation” for subtraction with regrouping. Another interesting feature of the Chinese teachers’ interviews was that they tended to address connections among mathematical topics. According to the Chinese teachers, the basic idea of subtraction with regrouping develops through several levels.
