原式=1/3+1/6+1/10+……+1/50×99
=2×(1/6+1/12+1/20+……+1/99×100)
=2×(1/2-1/3+1/3-1/4+1/4-1/5+……+1/99-1/100)
=2×(1/2-1/100)
=1-1/50
=49/50
原式=1/2/(3/2)+1/3/(3/2×4/3)+1/4/(3/2×4/3×5/4)+...+1/99/(3/2×4/3×5/4×...×100/99)
=1/2/(3/2)+1/3/(4/2)+1/4/(5/2)+...+1/99/(100/2)
=2/(2×3)+2/(3×4)+2/(4×5)+...+2/(99×100)
=2×(1/2-1/3)+2×(1/3-1/4)+2×(1/4-1/5)+...+2×(1/99-1/100)
=2×(1/2-1/100)
=49/50