基准数法.ppt

,单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,2019/12/10,#,一、基准数法,二、拆补凑整法,第二讲,1,下列算式怎样计算更简便？,（,1,）,3,3,3,3,3,3,（,2,）,7,7,7,7,7,7,7,（,3,）,6,6,6,6,6,6,5,（,4,）,9,8,8,8,8,8,课前活动,2,看谁算得快？,（,1,）,31,30,29,（,2,）,13,10,9,12,8,11,（,3,）,47,41,50,53,55,59,（,4,）,95,97,99,101,103,105,1.,基准数法,例题,1,3,1.,基准数法,（,1,）,38,39,41,42,（,2,）,88,86,90,91,92,（,3,）,92,88,93,89,91,（,4,）,100,101,102,103,练一练,4,1.,基准数法,（,1,）,101,98,97,100,105,（,2,）,67,58,62,55,63,60,例题,2,5,1.,基准数法,（,1,）,103,104,105,96,97,（,2,）,122,121,118,119,120,练一练,-,作业纸,6,几个接近数的加减运算,（,1,）,201,198,197,200,205,（,2,）,567,558,562,555,560,（,3,）,199,199,201,203,198,196,（,4,）,351,348,353,350,201,203,198,1.,基准数法,例题,3,7,1.,基准数法,（,1,）,101,98,97,100,105,（,2,）,301,305,298,300,297,（,3,）,501,503,496,499,493,（,4,）,203,204,202,205,98,97,99,练一练,8,1.,基准数法,某小组有,10,人，他们的数学成绩分别是,92,分、,88,分、,93,分、,89,分、,91,分、,90,分，求这个组的数学总成绩？,例题,4,9,1.,基准数法,某小组有,6,个人，他们的数学成绩分别为,92,分、,90,分、,88,分、,93,分、,91,分、,89,分，求这个组数学的总成绩？,练一练,10,加,补凑整,（,1,）,99999,9999,999,99,9,（,2,）,59997,3998,196,89,2,加减补凑整法,例题,5,11,2,加减补凑整法,（,1,）,9,19,199,1999,（,2,）,8,88,899,8999,练一练,12,加,补凑整（减法运用）,（,1,）,257,98,（,2,）,751,203,（,3,）,895,504,97,（,4,）,1034,399,102,2,加减补凑整法,例题,6,13,2,加减补凑整法,（,1,）,146,98,（,2,）,234,203,（,3,）,598,396,97,（,4,）,534,399,98,练一练,14,1.,基准数法：,a.,几个接近的数全部看作同一个整十数、整百数、整千数等，变加为乘。,2,.,加补凑整。,a.,每个数分别凑整，在计算。,15,