98*199
=(100-2)*(200-1)
=100*200-100-2*200+2
=20000-500+2
=19502
简便计算
98✖️199
=98x(200-1)
=98x200-98
=19600-98
=19502
98✖️199
=98✖️(200-1)
=98✖️200-98
=19600-98
=19502
原式=98*(200-1)
=98*200-98*1
=19600-98
=19502
乘法分配律为:两个数的和与一个数相乘,先将它们与这个数分别相乘,再相加,积不变.即:(a+b)×c=a×c+b×c.反过来则:a×c+b×c=(a+b)×c
把199变为200-1计算
98× 199
= 98× ( 200-1)
= 98×200-98
= 19600 -98
= 19502