024 74×76 = 5624 93×97 = 9021Р1、十同尾补Р7×(7+1) =56Р7Р4Р×Р7Р6Р=Р56Р24Р9×(9+1) =90Р9Р3Р×Р9Р7Р=Р90Р21Р35×35 = 1225 63×67 = 4221?42×48 = 2016 54×56 = 3024 74×76 = 5624 93×97 = 9021Р1、十同尾补Р35×34Р=1190Р≠Р1220Р43×44Р=1892Р≠Р2012Р( 5 + 5=10 )Р35×34=1190≠1220Р43×44=1892≠2012Р( 2 + 8=10 )Р( 3 + 7=10 )Р( 4 + 6=10 )Р( 3 + 7=10 )Р( 4 + 6=10 )Р( 5 + 4 = 9 )Р( 3 + 4 = 7 )Р1、十同尾补Р尾数互补Р3Р×Р3Р=Р12Р5Р5Р25Р6Р×Р6Р=Р42Р3Р7Р21Р4Р×Р4Р=Р20Р2Р8Р16Р5Р×Р5Р=Р30Р4Р6Р24Р7Р×Р7Р=Р56Р4Р6Р24Р9Р×Р9Р=Р90Р3Р7Р21Р33×37Р=12Р21Р55×55Р=30Р25Р71×79Р=56Р9Р09Р213×287 = 61131Р---- (13+87 = 100)Р213×287 = 61131Р2×( 2+1)Р33×37Р=12Р21Р55×55Р=30Р25Р71×79Р=56Р09Р201×209 = 42009Р---- ( 1+9=10 )Р201×209 = 42009Р20×( 20+1)Р熟练记忆以下算式及结果:Р15×15=225 65×65=4225?25×25=625 75×75=5625?35×35=1225 85×85=7225?45×45=2025 95×95=9025?55×55=3025 105×105=11025
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