早教吧 育儿知识 作业答案 考试题库 百科 知识分享

用简便方法计算:(要写出计算过程)429+202278+99582-103804-397.

题目详情
用简便方法计算:(要写出计算过程)
429+202       278+99      582-103         804-397.
▼优质解答
答案和解析
(1)429+202
=429+(200+2)
=(429+200)+2
=629+2
=631     

(2)278+99 
=278+(100-1)
=(278+100)-1
=378-1
=377
     
(3)582-103
=592-(100+3)
=592-100-3
=492-3
=489         

(4)804-397
=804-(400-3)
=804-400+3
=404+3
=407