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案例三年级下学期,学生学习了乘法估算。在一次练习中,我设计了这样一道题目:18×22≈()。学生独立完成,汇报时主要有下面三种方法:方法一:18×22≈(440)↓20方法二:18×22≈(360)↓20方法三:18×22≈(400)↓↓20 20师:方法一约等于440,实际结果比估算结果大还是小呢?生(异口同声):小。师:为什么?生:因为把18估成20是往大了估,所以实
In the third grade of the case, students study the multiplication estimate. In a practice, I designed such a topic: 18 × 22 ≈ (). Students complete independently and report the following three methods: Method 1: 18 × 22 ≈ (440) ↓ 20 Method 2: 18 × 22 ≈ (360) ↓ 20 Method 3: 18 × 22 ≈ (400) ↓↓ 20 20 division: a method is about equal to 440, the actual results larger than the estimated result or small? Health (in unison): small. Teacher: Why? Health: Because 18 is estimated to be greatly assessed 20, so real