201.1乘1999-2012 乘199.8的简便计算
问题描述:
201.1乘1999-2012 乘199.8的简便计算
答
201.1×1999-2012 ×199.8=2011×199.9-2012 ×199.8=(2012-1)×199.9-2012 ×199.8=2012×199.9-199.9-2012 ×199.8=2012×(199.9-199.8)-199.9=2012×0.1-199.9=201.2-199.9=1.3