899998+89998+8998+898 123+234+345+456+567+678 请说出解答技巧.
3个回答

(1) 899998+89998+8998+898

=(900000-2)+(90000-2)+(9000-2)+(900-2)

=900000+90000+9000+900-8

=999900-8

=999892

(2)123+234+345+456+567+678

=(123+567)+(234+456)+{345+(675+3)}

=690+690+1020+3

=690+690+(1000+10+10)+3

=690+10+690+10+1000+3

=700+700+1000+3

=2403

方法你肯定能看出来,不用我说了.