用简便方法计算:123+234+345+456+567+678+789急
来源:学生作业帮 编辑:搜搜做题作业网作业帮 分类:数学作业 时间:2024/05/02 02:38:58
用简便方法计算:123+234+345+456+567+678+789急
123+234+345+456+567+678+789
=(123+789)+(234+678)+(345+567)+456
=2X456+2X456+2X456+456
=7X456
=3192
=(123+789)+(234+678)+(345+567)+456
=2X456+2X456+2X456+456
=7X456
=3192