1/2×1/3+1/3×1/4+1/4×1/5+....+1/99×1/100
=1/6+1/12+1/20+...+1/9900
=1/2*3+1/3*4+1/4*5+...+1/99*100
=1/2-1/3+1/3-1/4+1/4-1/5+...+1/99-1/100
=1/2-1/100
=49/100
(好像是这样的,不知道有没有算错)
1/2×1/3+1/3×1/4+1/4×1/5+....+1/99×1/100
=1/2-1/3+1/3-1/4+1/4-1/5+------+1/99-1/100
=1/2-1/100
=49/100
1/n×1/(n+1)=1/n-1/(n+1)
所以:
1/2×1/3+1/3×1/4+1/4×1/5+....+1/99×1/100
=1/2-1/3+1/3-1/4+...+1/99-1/20
=1/2-1/100
=49/100
54