6.2×1.02 =6.2*1+6.2*0.02=6.3241.25*99=1.25*100-1.25=125-1.25=123.7512.5*32*2.5=12.5*8*4*2.5=100*10=10004.12-1.78-1.22=4.12-（1.78+1.22）=4.12-3=1.12（4.2/0.7）/6=4.2/（0.7*6）=4.2/4.2=1抱歉第一题我打错了是6.25×1.02...=。=6.25*1.02=6.25*1+6.25*0.02=6.25+0.125=6.375能不能说一下12.5*(0.7*0.8)简便计算原式=12.5*0.8*0.7=10*0.7=7