用简便方法计算:123+234+345+456+567+678+789急_数学解答

用简便方法计算:123+234+345+456+567+678+789急

人气：233 ℃　时间：2019-08-19 11:24:43

解答

123+234+345+456+567+678+789
=（123+789）+（234+678）+（345+567）+456
=2X456+2X456+2X456+456
=7X456
=3192