SEAMO X 2019 — Paper E — Grade 9–10 Question 5

Evaluate $N=\displaystyle\prod_{j=1}^{1009}\frac{\frac1{2j}-\frac1{2j+1}}{\frac1{2j+1}-\frac1{2j+2}}$. The first factors use $2,3,4$ and $4,5,6$; the last uses $2018,2019,2020$.