1 + 1 +2 分之1+ 1+2+3分之1 +(省略号)+1+2+3+(省略号)+100分之1
问题描述:
1 + 1 +2 分之1+ 1+2+3分之1 +(省略号)+1+2+3+(省略号)+100分之1
答
原式=(1+1/3+1/6+…+1/5050)*(1/2)/(1/2)
=(1/2+1/6+…+1/10100)/(1/2)
=(1-1/2+1/2-1/3+…+1/100-1/101)/(1/2)
=200/100
答
∵1+2=2*3/2
1+2+3=3*4/2
1+2+3+4=4*5/2
......
1+2+3+……+100=100*101/2
∴1+1/(1+2)+1/(1+2+3)+1/(1+2+3+4)+...+1/(1+2+3+...+100)
=1+2/(2*3)+2/(3*4)+2/(4*5)+……+2/(100*101)
=2[(1/2+1/(2*3)+1/(3*4)+1/(4*5)+……+1/(100*101)〕
∵1/(2*3)=1/2-1/3;
1/(3*4)=1/3-1/4;
1/(4*5)=1/4-1/5;
… …
1/(100*101)=1/100-1/101
∴原式=2(1/2+1/2-1/3+1/3-1/4+1/4-1/5+……+1/100-1/101)
=2[1+(-1/3+1/3)+(-1/4+1/4)+(-1/5+1/5)……(-1/100+1/100)-1/101 ]
=2(1-1/101)
=2*100/101
=200/101