2016分数乘法例例.ppt

求几个相同加数的和的简便运算 观察特点 计算下列各题就是先约分再计算，计算结果必须是最简分数。 计算下列各题 * —分数乘整数 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.复 习: （1）5个12是多少？怎样列式? （2）4个0.5的和是多少？ （3） Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. （一共20个） 1、 2、 3、 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 分数乘整数的意义是什么？分数乘整数的意义与整数乘法的意义相同，就是求几个相同加数的和的简便运算。 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 人跑一步的距离相当于袋鼠跳一下的。 11 2 人跑3步的距离是袋鼠跳一下的几分之几？ 11 2 ? 11 2 11 2 袋鼠跳一下 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 求三个相同加数的和。 ＝ 分母不变，分子相加。 ＝ 可以用 乘法计算吗？ ×3 ＝ ＝ Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 分子与整数相乘 分母不变分数乘整数，用分数的分子和整数相乘的积作分子，分母不变。 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 练习 1、看图写算式。 2 7 2 7 2 7 ＋ ＋ × = = 6 7 2 7 6 7 2 7 2 7 2 7 3 ＋ ＋ = ＋ ＋ = = × 1 4 1 4 1 4 3 4 1 4 3 3 4 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 2 9 4 还可以这样做： 3 4 3 4 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 3、分数乘整数的简便算法： Evalua