Simple calculation 1÷(1×2×3)+1÷(2×3×4)+1÷(3×4×5)+1÷(4×5×6)+.+1÷(98×99×100)

Simple calculation 1÷(1×2×3)+1÷(2×3×4)+1÷(3×4×5)+1÷(4×5×6)+.+1÷(98×99×100)

=(1/2)(1/1×2-1/2×3)+(1/2)(1/2×3-1/3×4)+…… +(1/2)(1/98×99-1/99×100)
=(1/2)(1/1×2-1/2×3+1/2×3-1/3×4+…… +1/98×99-1/99×100)
=(1/2)(1/1×2-1/99×100)
=4949/19800