100+99.9-99.8-99.7+99.6+99.5-99.4-99.3+…...+0.4+0.3-0.2-0.1
4个回答

(100-99.8)+(99.9-99.7)+(99.6-99.4)+.+(0.3-0.1)

=0.2*250

=50