1.2+2.125-3.2+4.125-5.2+……-99.2+100.125
=1.2-(3+5+7+...+99)-0.2*49+(2+4+6+...+100)+0.125*50
=1.2-49*(3+99)/2-9.8+50*(2+100)/2+6.25
=1.2-9.8+6.25+50*51-49*51
=48.65
1.2+2.125-3.5+4.125-5.2+……-99.2+100.125
1.2+2.125-3.2+4.125-5.2+……-99.2+100.125
=1.2-(3+5+7+...+99)-0.2*49+(2+4+6+...+100)+0.125*50
=1.2-49*(3+99)/2-9.8+50*(2+100)/2+6.25
=1.2-9.8+6.25+50*51-49*51
=48.65