csat-suneung 2025 Q18

csat-suneung · South-Korea · csat__math 3 marks Arithmetic Sequences and Series Compute Partial Sum of an Arithmetic Sequence
A sequence $\left\{ a_{n} \right\}$ satisfies $$a_{n} + a_{n+4} = 12$$ for all natural numbers $n$. What is the value of $\sum_{n=1}^{16} a_{n}$? [3 points]
A sequence $\left\{ a_{n} \right\}$ satisfies
$$a_{n} + a_{n+4} = 12$$
for all natural numbers $n$. What is the value of $\sum_{n=1}^{16} a_{n}$? [3 points]