1/1*3=1/2(1-1/3)
1/3*5=1/2(1/3-1/5)
.
1/99*101=1/2(1/99-1/101)
原式=1/2(1-1/3+1/3-1/5+1/5-1/7+.+1/99-1/101)
=1/2(1-1/101)
=1/2*100/101
=50/101
1/1*3=1/2(1-1/3)
1/3*5=1/2(1/3-1/5)
.
1/99*101=1/2(1/99-1/101)
原式=1/2(1-1/3+1/3-1/5+1/5-1/7+.+1/99-1/101)
=1/2(1-1/101)
=1/2*100/101
=50/101