原式=1+2+……+49+(0.5+1.5)+(2.5+3.5)+(4.5+5.5)+(48.5+49.5)
=(1+49)*49*0.5+2+6+……+98
=25*49+(2+98)*0.5*25
=25*49+50*25
=25*99
=2475
原式=1+2+……+49+(0.5+1.5)+(2.5+3.5)+(4.5+5.5)+(48.5+49.5)
=(1+49)*49*0.5+2+6+……+98
=25*49+(2+98)*0.5*25
=25*49+50*25
=25*99
=2475