50乘以40怎么算

29乘以30+30乘以31+31乘以32-----49乘以50怎么简算 四乘以12.25%乘以2乘以0.3怎么算 五年级 0.15乘以0.8乘以12.5加8乘以3乘以0.125怎么简便算 10乘以20乘以30乘以40乘以50乘以60乘以70乘以80乘以90乘以100等于多少 125乘以64乘以25巧算怎么算,急 209209乘以208减208208乘以209 怎么巧算? 54乘以45加90乘以23怎么巧算 0.9乘以4.2乘以9.1用简便算法怎么算 99乘以100减去98乘以19怎么简算 怎么简算13.5乘以10.1加6.5乘以9.9 7.5乘以23加31乘以2.5怎么简算 2013乘以20142014减去2012乘以20132013 怎么简算?