如题所述
第1个回答 2017-04-26
99X31
=(100-1)×31
=100×31-31
=3100-31
=3069本回答被网友采纳
=(100-1)×31
=100×31-31
=3100-31
=3069本回答被网友采纳
第2个回答 2017-04-26
99*31
=(100-1)*31
=31*100-31*1
=3100-31
=3069
=(100-1)*31
=31*100-31*1
=3100-31
=3069