错？4.5×0.8= 0.45×99？？？？？？？？？不是啦，是三题：4.5×0.8=(4+0.5)×0.8=. 2.3×0.25+1.7×0.25=0.45×99=4.5×0.8=(4+0.5)×0.8=4X0.8+0.5x0.8=3.2+0.4=3.6 2.3×0.25+1.7×0.25=0.25X（2.3+1.7）=0.25X4=1 0.45×99=0.45x(100-1)=0.45X100-0.45X1=45-0.45=44.55