解:100+200+300+400……………………+10000
=(1+2+······+100)x100
=【(1+100)x100÷2】x100
=5050x100
=505000
原式
=(100+10000)×100÷2
=10100×50
=505000
(首项+末项)*项数/2=505000
-----精锐教育五角场校区
=100*(1+2+3+·····+100)
=100*5050
=505000
1+2+3+···+100
=(1+100)+(2+99)+(3+98)···+(50+51)
=101*50
=5050