SEAMO 2019 — Paper E — Grade 9–10 Question 22

Arithmetic sequences $\{a_n\},\{b_n\}$ satisfy $a_1=2019$, $b_1=1$, $a_{100}+b_{100}=1010$. Find $a_1+\cdots+a_{20}+b_1+\cdots+b_{20}$.