三年级数学下册除法估算兖州市小孟镇桑园小学陈衍福.ppt

除法估算人教新课标三年级数学下册兖州市小孟镇桑园小学陈衍福 Evaluation only. Evaluation only. Created with Client Profile . Created with Client Profile . Copyright 2004-2011 Aspose Pty Ltd. Copyright 2004-2011 Aspose Pty Ltd. 。 18 ÷ 6 = 32 ÷ 4 = 270 ÷ 3 = 560 ÷ 8 = 200 ÷ 4 = 300 ÷ 5 = 400 ÷ 8 = 1200 ÷ 3 = 2000 ÷ 4 = 8000 ÷ 2 = 9000 ÷ 3 = 1500 ÷ 5 = 。(1) 450 除以 5得多少? (2)被除数是 2800 ,除数是 7,商是多少? 。 49 ≈ 91 ≈ 152 ≈ 198 ≈ 38 50 500 60 4000 3000 300 400 90 50 70 450 ÷ 5 = 90 2800 ÷ 7 = 400 50 150 200 90 Evaluation only. Evaluation only. Created with Client Profile . Created with Client Profile . Copyright 2004-2011 Aspose Pty Ltd. Copyright 2004-2011 Aspose Pty Ltd. 提出问题:李叔叔他们三人,平均每人运多少箱? 问题变换如何算出李叔叔他们三人平均每人大约运多少箱? Evaluation only. Evaluation only. Created with Client Profile . Created with Client Profile . Copyright 2004-2011 Aspose Pty Ltd. Copyright 2004-2011 Aspose Pty Ltd. 124 ÷ 3 ≈__ (箱) 方法一: 124 ≈ 120 , 120 ÷ 3=40 , 所以 124 ÷ 3 ≈ 40 。方法二: 124 = 120+4 , 120 ÷ 3=40 ,剩下的 4箱每人再运一箱。 40+1=41 同一个问题,有不同的解答方法,虽然估算的结果不同, 但是两种结果都是合理的、正确的。方法二更精确一点。 Evaluation only. Evaluation only. Created