Question

巧算 123+234+345—456+567+678+789—890

Answer 1

123+234+345+456+567+678+789

=123*7+111*(1+2+3+4+5+6)=123*7+111*21=3192

或

123+234+345+456+567+678+789

==(100+700)*(7/2)+(20+80)*(7/2)+(3+9)*(7/2)

=800*(7/2)+100*(7/2)+12*(7/2)

=(800+100+12)*(7/2)

=912*(7/2)

=456*7

=3192