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第,3,招 巧算加减法,学习第,7,单元后使用,QD,四年级上册,将,48,里面拆出前面所需的数与前面的数凑整。,计算：,49998,4998,498,48,方法一,:,“拆小补大”,方法二：采用凑整的方法解题,每一个数都接近整十、整百、整千、整万,经典例题,规范解答：,解法一：,49998,4998,498,48,(49998,2),(4998,2),(498,2),(48,2,2,2),50000,5000,500,42,55542,解法二：,49998,4998,498,48,(49998,2),(4998,2),(498,2),(48,2),24,50000,5000,500,50,8,55542,1,2,3,4,提示,：,点击 进入题组训练,用加法运算律进行简算,用减法的性质简算,用凑整法简算,用基准数法简算,1,简算。,(1)183,35,365,(2)92,94,108,206,用加法运算律进行简算,技 巧,1,183,(35,365),183,400,583,(92,108),(94,206),200,300,500,(3)8897,128,597 (4)132,85,68,8897,597,128,8300,128,8428,132,68,85,200,85,115,用减法的性质简算,技 巧,2,2,简算。,(1)462,(262,129),(2)800,198,102,462,262,129,200,129,71,800,(198,102),800,300,500,(3)632,136,232 (4)324,(124,97),632,232,136,400,136,264,324,124,97,200,97,297,用凑整法简算,技 巧,3,3,简算。,(1)9,99,999,9999,99999,10,100,1000,10000,100000,5,111110,5,111105,(9,1),(99,1),(999,1),(9999,1),(99999,1),15,(2)19,298,3997,49996,599995,(19,1),(298,2),(3997,3),(49996,4),(599995,5),15,20,300,4000,50000,600000,15,654320,15,654305,用基准数法简算,技 巧,4,4,简算。,(1) 71,69,68,73,74,70,68,707,1,1,2,3,4,2,493,70,1,70,1,70,2,70,3,70,4,70,70,2,以,70,为基准变化,(2)473,468,467,466,464,469,474,465,471,473,47010,3,2,3,4,6,1,4,5,1,3,4700,10,4690,以,470,为基准变化,470,3,470,2,470,3,470,4,470,6,470,1,470,4,470,5,470,1,470,3,
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