六年级数学奥数题1 1 3 1 6 1 10 1 15 1 5050（六年级上册数学奥数题100道）

1+1/3+1/6+1/10+1/15 =2(1/1-1/2)+2(1/2-1/3)+2(1/3-1/4)+2(1/5-1/6)+...+2(1/100-1/101) =2(1/1-1/2+1/2-1/3+1/3-1/4+1/5-1/6+...+1/100-1/101) =2(1/1-1/101) =2*100/101 =200/101