第十二讲 一个苹果等于几个梨（二）
一、专题简析：
数学上有许多重大的发现和疑难问题的解决都离不开推理，学会了推理，能使小朋友们头脑更灵活，变得更聪明。这节课我们共同研究简单推理的初步知识，今后我们将进一步地去学习，希望大家能够多观察、多动脑、多分析，培养我们的观察能力和分析能力。仔细的观察、分析，弄清两组物品之间的相等关系，将这种关系代入另一组当中，就可明白问题中两个物品之间的关系了。
二、综合讲解：
[例1]
= =![](https://wkrtcs.bdimg.com/rtcs/image?w=58.28&md5sum=166ef870f6bdb629919a5d2b36a10c7d&sign=a5113e6e55&rtcs_flag=2&rtcs_ver=3&l=webapp&bucketNum=113&ipr={"t":"img","r":"r_9","w":"58.28","h":"26.79","dataType":"gif","c":"word/media/image1.gif"})
=（ ）个 ![](https://wkrtcs.bdimg.com/rtcs/image?w=23.67&md5sum=166ef870f6bdb629919a5d2b36a10c7d&sign=a5113e6e55&rtcs_flag=2&rtcs_ver=3&l=webapp&bucketNum=113&ipr={"t":"img","r":"r_11","w":"23.67","h":"22.33","dataType":"gif","c":"word/media/image3.gif"})
讲解： 由图知道，1个圆=6个方块，1个圆=1个三角和4个方块，我们发现多了1个三角，少了2个方块，说明1个三角=2个方块，也就是2个方块可以换1个三角，那么6个方块就可以换3个三角，因为1个圆=6个方块，所以1个圆=3个三角。
[例2] （1） －4＝6 ＝（ ）![](https://wkrtcs.bdimg.com/rtcs/image?w=14.74&md5sum=166ef870f6bdb629919a5d2b36a10c7d&sign=a5113e6e55&rtcs_flag=2&rtcs_ver=3&l=webapp&bucketNum=113&ipr={"t":"img","r":"r_14","w":"14.74","h":"12.28","dataType":"gif","c":"word/media/image5.gif"})
＋ ＝13 ＝（ ） ![](https://wkrtcs.bdimg.com/rtcs/image?w=14.51&md5sum=166ef870f6bdb629919a5d2b36a10c7d&sign=a5113e6e55&rtcs_flag=2&rtcs_ver=3&l=webapp&bucketNum=113&ipr={"t":"img","r":"r_14","w":"14.51","h":"24.56","dataType":"gif","c":"word/media/image6.gif"})
（2）9＋ ＝10 ＝（ ）![](https://wkrtcs.bdimg.com/rtcs/image?w=12.96&md5sum=166ef870f6bdb629919a5d2b36a10c7d&sign=a5113e6e55&rtcs_flag=2&rtcs_ver=3&l=webapp&bucketNum=113&ipr={"t":"img","r":"r_18","w":"12.96","h":"22.33","dataType":"gif","c":"word/media/image7.gif"})
－ ＝10 ＝（ ）![](https://wkrtcs.bdimg.com/rtcs/image?w=12.96&md5sum=166ef870f6bdb629919a5d2b36a10c7d&sign=a5113e6e55&rtcs_flag=2&rtcs_ver=3&l=webapp&bucketNum=113&ipr={"t":"img","r":"r_14","w":"12.96","h":"22.33","dataType":"gif","c":"word/media/image9.gif"})
讲解：（1）因为 －4＝6，所以 ＝4＋6＝10 。又因为![](https://wkrtcs.bdimg.com/rtcs/image?w=14.74&md5sum=166ef870f6bdb629919a5d2b36a10c7d&sign=a5113e6e55&rtcs_flag=2&rtcs_ver=3&l=webapp&bucketNum=113&ipr={"t":"img","r":"r_14","w":"14.74","h":"17.86","dataType":"gif","c":"word/media/image11.gif"})
＋10=13，所以 ＝13－10=3 ![](https://wkrtcs.bdimg.com/rtcs/image?w=14.74&md5sum=166ef870f6bdb629919a5d2b36a10c7d&sign=a5113e6e55&rtcs_flag=2&rtcs_ver=3&l=webapp&bucketNum=113&ipr={"t":"img","r":"r_14","w":"14.74","h":"24.56","dataType":"gif","c":"word/media/image13.gif"})
（2）因为9＋ ＝10，所以 ＝10－9＝1。
又因为 -1=10，所以 =10＋1=11![](https://wkrtcs.bdimg.com/rtcs/image?w=25.01&md5sum=166ef870f6bdb629919a5d2b36a10c7d&sign=a5113e6e55&rtcs_flag=2&rtcs_ver=3&l=webapp&bucketNum=113&ipr={"t":"img","r":"r_1","w":"25.01","h":"22.33","dataType":"gif","c":"word/media/image14.gif"})
3、运用与提高
1、
![](https://wkrtcs.bdimg.com/rtcs/image?w=304.00&md5sum=166ef870f6bdb629919a5d2b36a10c7d&sign=a5113e6e55&rtcs_flag=2&rtcs_ver=3&l=webapp&bucketNum=113&ipr={"t":"img","r":"r_6","w":"304.00","h":"185.33","dataType":"gif","c":"word/media/image16.gif"})
2、 +5 = 12 =（ ）![](https://wkrtcs.bdimg.com/rtcs/image?w=25.33&md5sum=166ef870f6bdb629919a5d2b36a10c7d&sign=a5113e6e55&rtcs_flag=2&rtcs_ver=3&l=webapp&bucketNum=113&ipr={"t":"img","r":"r_1","w":"25.33","h":"22.67","dataType":"gif","c":"word/media/image15.gif"})
+ =20 =（ ）![](https://wkrtcs.bdimg.com/rtcs/image?w=14.67&md5sum=166ef870f6bdb629919a5d2b36a10c7d&sign=a5113e6e55&rtcs_flag=2&rtcs_ver=3&l=webapp&bucketNum=113&ipr={"t":"img","r":"r_3","w":"14.67","h":"24.00","dataType":"gif","c":"word/media/image18.gif"})
3、 - = 10 =（ ） ![](https://wkrtcs.bdimg.com/rtcs/image?w=24.00&md5sum=166ef870f6bdb629919a5d2b36a10c7d&sign=a5113e6e55&rtcs_flag=2&rtcs_ver=3&l=webapp&bucketNum=113&ipr={"t":"img","r":"r_2","w":"24.00","h":"22.67","dataType":"gif","c":"word/media/image17.gif"})
20- =6 =( )![](https://wkrtcs.bdimg.com/rtcs/image?w=13.33&md5sum=166ef870f6bdb629919a5d2b36a10c7d&sign=a5113e6e55&rtcs_flag=2&rtcs_ver=3&l=webapp&bucketNum=113&ipr={"t":"img","r":"r_1","w":"13.33","h":"22.67","dataType":"gif","c":"word/media/image20.gif"})
2. + =6 =( )![](https://wkrtcs.bdimg.com/rtcs/image?w=25.33&md5sum=166ef870f6bdb629919a5d2b36a10c7d&sign=a5113e6e55&rtcs_flag=2&rtcs_ver=3&l=webapp&bucketNum=113&ipr={"t":"img","r":"r_1","w":"25.33","h":"22.67","dataType":"gif","c":"word/media/image14.gif"})
+ =8 = ( )![](https://wkrtcs.bdimg.com/rtcs/image?w=14.67&md5sum=166ef870f6bdb629919a5d2b36a10c7d&sign=a5113e6e55&rtcs_flag=2&rtcs_ver=3&l=webapp&bucketNum=113&ipr={"t":"img","r":"r_3","w":"14.67","h":"24.00","dataType":"gif","c":"word/media/image21.gif"})
+ + =12 = ( )![](https://wkrtcs.bdimg.com/rtcs/image?w=13.33&md5sum=166ef870f6bdb629919a5d2b36a10c7d&sign=a5113e6e55&rtcs_flag=2&rtcs_ver=3&l=webapp&bucketNum=113&ipr={"t":"img","r":"r_2","w":"13.33","h":"22.67","dataType":"gif","c":"word/media/image20.gif"})
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