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一、透过案例看估算的现状【案例一】从大赛看估算的实施,纯粹为了估算而估算。近日,有幸观摩了某十省区的小学数学优质课大赛。有一节是人教版四年级上册的三位数乘两位数,其中的几个有关估算环节本人不敢苟同。1、复习环节。①估算17×28生1:17×28≈600生2:17×28≈510②笔算17×28。由于两位数乘两位数是学过的知识,所以学生很快通过竖式计算出积是476。接着教师小结算法后出示新授内容情境。在这儿,教师为何不把估算的结果与笔算的积作比较呢!使估算孤苦伶仃,师生视而不见。
First, through the case to see the status of estimation [Case I] from the contest to see the implementation of estimates, pure estimates for the estimation. Recently, fortunate enough to observe the primary school mathematics in a certain province of quality competitions. There is a section of the PEP fourth grade three-digit by two figures, several of which I personally can not agree with the estimation section. 1, review the link. ① estimated 17 × 28 students 1: 17 × 28 ≈ 600 students 2: 17 × 28 ≈ 510 笔 pen calculation 17 × 28. Since double-digit multiples are learned, the student quickly calculates that the plot is 476 by vertical calculation. Then the teacher summarizes the algorithm to produce a new content context. Here, why teachers do not compare the result of the estimation with the sum of the calculation of the pen! Make the estimation lonely, teachers and students turn a blind eye.