很高兴为你解答!99.9*77.8-33.3*66.6=99.9*77.8-33.3*3*22.2=99.9*(77.8-22.2)=99.9*55.6=(100-0.1)*55.6=556-5.56=550.44
这个题目的话可以先把99.9变成100-0.1然后33.3×66.6变成99.9×22.2。
99.9×(77.8-22.2)=99.9×55.6=(100-0.1)×55.6=5560-5.56=5554.44