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在教学人教版二年级下册第七单元中整千、整百数的加减法时,笔者发现学生其实都会算,算理也说得头头是道,比如计算3000+5000,“先不看3和5后面的0,把3和5加起来等于8,再把3个0还回去,就等于8000。”老师引一引:“为什么3和5能加在一起?”学生也都知道:“3表示3个干,5表示5个千,它们都表示几个干,所以能加在一起。”“3在千位,5也在千位,所以能加在一起。”……老师再点一点,算理说起来就很清楚了:3个千加5个千是8个千,也就是8000。可是
Teaching PEP 2 second grade seventh unit in the whole thousand, the whole hundred addition and subtraction method, I found that students actually will count, arithmetic also put it bluntly, such as calculating 3000 + 5000, 3 and 5 behind 0, the sum of 3 and 5 is equal to 8, and then 3 0 back, it is equal to 8000. “The teacher cited a lead: ” Why 3 and 5 can be together? “Students All know: ”3 said 3 dry, 5 said 5 thousand, they all said a few dry, so can be added together. “ ”3 thousands, 5 is thousands, so can be added together . "... ... The teacher a little more, the calculation is very clear: three thousand plus five thousand is eight thousand, which is 8000. but