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8+9=5+9=9+4=17-9=14-9=13-9=,一、快速口算,17,14,8,4,13,5,13-9=4,方法三:9+(4)=13 13-9=4(想加算减),方法一:13-3=10 10-6=4(平十法),方法二:10-9=1 1+3=4(破十法),十几减8、7,拿走8把,还剩多少把?,15-8=,?,拿走8根,还剩多少根?,158,7,想:,1082,2+57,158,7,想:,15510,1037,158,7,想:,8+()15,1587,7,8,6,4,4,7,7,4,7,6,9,3,11,17,5,9,12,5,4,8,7,6,118,128,138,148,158,168,178,3,4,5,6,7,8,9,117,127,137,147,157,167,177,4,5,6,7,8,9,10,0.25,谢谢!,