Question

45Ⅹ15十45X24十25的简便计算？

Answer 1

45×3+24×9+5×5＝5×（135+2165）＝5×356＝1780

Answer 2

（25+20）×15+（25+20）×24+25
=25×15+20×15+25×24+20×24+25
=25×（15+24+1）+20×（15+24）
=25×40+20×39
=1000+780
=1780