1、C列分数化小数的记法:分子乘5,小数点向左移动两位。2、D、E两列分数化小数的记法:分子乘4,小数点向左移动两位常见分数、小数互化表A列B列C列D列E列5.021125.08105.020104.025152.0251325.041375.08315.020308.025256.0251475.043625.08535.020712.025364.02516875.08745.020916.025468.025172.0511.010155.0201124.025672.025184.0523.010365.0201328.025776.025196.0537.010785.0201732.025884.025218.0549.010995.0201936.025988.0252202.05010625.016144.0251192.0252301.0100148.0251296.02524常见的分数、小数及百分数的互化除法除不尽(按四舍五入计算)除法比分数小数百分除法比分数小数百分1÷21:21/20.550%1÷31:31/30.3333%1÷41:41/40.2525%2÷32:32/30.6767%1÷51:51/50.220%1÷61:61/60.1717%2÷52:52/50.440%5÷65:65/60.8383%3÷53:53/50.660%1÷71:71/70.1414%4÷54:54/50.880%2÷72:72/70.2929%1÷81:81/80.12512.5%3÷73:73/70.4343%3÷83:83/80.37537.5%4÷74:74/70.5757%5÷85:85/80.62562.5%5÷75:75/70.7171%7÷87:87/80.87587.5%6÷76:76/70.8686%1÷101:101/100.110%1÷91:91/90.1111%3÷103:103/100.330%2÷92:92/90.2222%7÷107:107/100.770%4÷94:94/90.4444%9÷109:109/100.990%5÷95:95/90.5656%3÷23:23/21.5150%7÷97:97/90.7878%5÷45:45/41.25125%8÷98:98/90.8989%7÷57:57/51.4140%4÷34:34/31.33133%备注除尽是指除数(前项、分子)除以除数(后项、分母)得商不出现循环(或无限循环)小数;除不尽与除尽相反,是无限循环小数。常用平方数11²=12112²=14413²=16914²=19615²=22516²=25617²=28918²=32419²=36120²=40021²=44122²=48423²=52924²=57625²=62526²=67627²=72928²=78429²=84130²=90031²=96132²=102433²=108934²=115635²=122536²=129637²=136938²=144439²=152140²=160041²=168142²=176443²=184944²=193645²=202546²=211647²=220948²=230449²=240150²=2500常见立方数1³=12³=83³=274³=645³=1256³=2167³=3438³=5129³=729常见特殊数的乘积25×3=7525×4=10025×8=200125×3=375125×4=500125×8=1000625×16=1000037×3=111错位相加/减A×9型速算技巧:A×9=A×10-A;例:743×9=743×10-743=7430-743=6687A×9.9型速算技巧:A×9.9=A×10+A÷10;例:743×9.9=743×10-743÷10=7430-74.3=7355.7A×11型速算技巧:A×11=A×10+A;例:743×11=743×10+743=7430+743=8173A×101型速算技巧:A×101=A×100+A;例:743×101=743×100+743=75043乘/除以5、25、125的速算技巧:A×5型速算技巧:A×5=10A÷2;例:8739.45×5=8739.45×10÷2=87394.5÷2=43697.25A÷5型速算技巧:A÷5=0.1A×2;例:36.843÷5=36.843×0.1×2=3.6843×2=7.3686A×25型速算技巧:A×25=100A÷4;例:7234×25=7234×100÷4=723400÷4=180850A÷25型速算技巧:A÷25=0.01A×4;例:3714÷25=3714×0.01×4=37.14×4=148.56A×125型速算技巧:A×5=1000A÷8;例:8736×125=8736×1000÷8=8736000÷8=1092000A÷125型速算技巧:A÷1255=0.001A×8;例:4115÷125=4115×0.001×8=4.115×8=32.92减半相加:A×1.5型速算技巧:A×1.5=A+A÷2;例:3406×1.5=3406+3406÷2=3406+1703=5109“首数相同尾数互补”型两数乘积速算技巧:积的头=头×(头+1);积的尾=尾×尾例:23×27=首数均为2,尾数3与7的和是10,互补所以乘积的首数为2×(2+1)=6,尾数为3×7=21,即23×27=621本方法适合11~99所有平方的计算。11X11=12121X21=414131X31=96141X41=168112X12=14822X22=48432X32=102442X42=176452X52=2704从上面的计算我们可以得出公式:个位=个位×个位所得数的个位,如果满几十就向前进几,十位=个位×(十位上的数字×2)+进位所得数的末位,如果满几十就向前进几,百位=两个十位上的数字相乘+进位。例:26×26=个位=6×6=36,满30向前进3;十位=6×(2×2)+3=27,满20向前=进2;百位=2×2+2=6由此可见26×26=6...