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二年级数学思维秋季班方法讲义:第 二 讲 按规律填数姓名 方法点播:我们经常会看到按一定规律排列起来的一列数,如果要接在一列数后面再写几个数,就要仔细观察这列数中已经出现的几个数之间有什么规律,找准了规律,就能按规律接下去填数了。按规律填数不是很容易就填对的,要运用数的顺序和加、减、乘、除法的知识,通过仔细观察,根据同组数排列的顺序和前后、上下之间的相互关系,才能找出数与数间的排列规律。【典型例题】【例1】按规律填数。(1) 1, 3, 5, 7, 9, ( ), ( ), 15, 17 (2) 1, 2, 4, 8, ( )练习1:(1)20, 18, 16, 14, ( ), ( ), 8, 6, 4(2)1, 7, 13, 19, ( ), ( ), 37, 43(3) 40, 35, 30, 25, ( ), ( ), 10, 5(4) 16, 8, 4, 2, ( )【例2】仔细观察,找规律填数。15, 3, 12, 3, 9, 3, ( ), ( )练习2: 19, 9, 17, 8, 15, 7, ( ), ( )【例3】 1, 1, 2, 3, 5, 8, ( ), ( )练习3:1, 3, 4, 7, 11, ( ), ( )【例4】1, 4, 9, ( ), ( ), 36练习4: 81, ( ), 49, 36, ( )【例5】 1, 2, 4, 7, 11, ( ), ( ), 29练习5:(1)15, 16, 19, 24, 31, ( ), ( )(2) 2, 5, 6, 9, 10, 13, 14, ( ), ( )(3) 32, 1, 16, 2, 8, 3, 4, ( ), ( )4271395317861(4)(5)16141215129954816261814 【课后巩固】1、按规律填数(1)19, 16, 13, 10, ( ), ( )(2)80, 70, ( ), ( ), 40, 30(3)5, 9, 13, ( ), 21,( ) (4)24, 20, ( ), ( ), 8, 4, 0(5)0, 3, 8, 15, 24, ( ), ( )(6)1, 2, 4, 5, 7, 8, 10, ( ), ( )(7)5, 3, 10, 5, 15, 7, ( ), ( )(8)20, 6, 17, 6, 14, 6, ( ), ( )(9)1, 1, 3, 7, 13, ( ), ( )(10)11 ,6 ,13 ,9 ,15 ,12 , ( ), ( )(11)2, 3, 5, 8, 13, ( ), ( )(12)1, 6, 16, 31, 51, ( ), ( )(13)3, 4, 7, 11, 18, 29, ( ), ( )(14)198, 297, 396, 495, ( ), ( )(15)2345, 3452, 4523, ( ), ( )(16)113410486614352、下面哪个数写错了,应该换上什么数?(1)90, 75, 60, 45, 30, 15, 1(2)0, 14, 28, 42, 56, 71, 86家长签字:
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