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1、常见分数、小数互化表C列分数化小数的记法：分子乘5，小数点向左移动两位。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
2、=1764432=1849442=1936452=2025462=2116472=2209482=2304492=2401502=2500完全平方数的记忆技巧：(a+b)2=a2+b2+2ab (ab)2=a2+b22ab五组常见的勾股数：32+42=52 ；52+122=132 ；72+242=252 ；82+152=172 ；202+212=292常用立方数53=12563=21673=34383=51293=72911=133112=172813=219714=274415=337516=409617=491318=583219=685921=9261常用特殊数的乘积2537525410
3、025820012533751254500125810006251610000373=111常用的倍13.141134.542165.9426.281237.682269.0839.421340.822372.22412.561443.962475.36515.71547.12578.5618.841650.242681.64721.981753.382784.78825.121856.522887.92928.261959.662991.061031.42062.83094.262113.04112379.94162803.8472153.86122452.16172907.4682200.
4、96132530.661821017.3692254.34142615.441921133.54102314152706.52021256速算技巧A9型A9=A10A7439=7430743=6687A9.9型A9.9=A10+A107439.9=743074.3=7355.7A11型A11=A10+A74311=7430+743=8173A101型A101=A100+A743101=74300+743=75043A5型A5=10A28739.455=87394.52=43697.25A5型A5=0.1A236.8435=3.68432=7.3686A25型A25=100A4723425=4=
5、A 25型A25=0.01A4371425=37.144=148.56A125型A125=1000A88736125=8=A125型A125=0.001A84115125=4.1158=32.92A1.5型A1.5=A+A234061.5=340634062=340617035109“首数相同尾数互补”型乘积积的头头(头+1)积的尾=尾尾2327：首数均为2，尾数37=10互补；积的头为2(21)=6，尾为37=21，即621常用的分数、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121:21/20.550%131:31/30.3333%141:41/40
6、.2525%232:32/30.6767%151:51/50.220%161:61/60.1717%252:52/50.440%565:65/60.8383%353:53/50.660%171:71/70.1414%454:54/50.880%272:72/70.2929%181:81/80.12512.5%373:73/70.4343%383:83/80.37537.5%474:74/70.5757%585:85/80.62562.5%575:75/70.7171%787:87/80.87587.5%676:76/70.8686%1101:101/100.110%191:91/90.1111%3103:103/100.330%292:92/90.2222%7107:107/100.770%494:94/90.4444%9109:109/100.990%595:95/90.5656%323:23/21.5150%797:97/90.7878%545:45/41.25125%898:98/90.8989%757:57/51.4140%434:34/31.33133%
