1/3×5 +1/5×7 + 1/7×9 + …+ 1/99×101
=1/2×(1/3-1/5)+1/2×(1/5-1/7)+……+1/2×(1/99-1/101)
=1/2×(1/3-1/5+1/5-1/7……1/99-1/101)
=1/2×(1/3-1/101)
=49/303