根據1+2+3+4+······+n=n(n+1)/2計算2+4+6+····+200

根據1+2+3+4+······+n=n(n+1)/2計算2+4+6+····+200

2+4+6+····+200=2*(1+2+……+100)=2*100*(100+1)/2=10100