nth term = S_n − S_(n−1)

CAT has tested this idea 3 times across 3 papers, from 2018 to 2022. Solve one, and the others are the same method with different numbers or wording, which is why repeated concepts are the most efficient thing to practise.

Question	What it asks	Answer
CAT 2018 Slot 2 · QA Q5	S_n = 2n^2 + 9n + 13; which term is 103	24
CAT 2022 Slot 1 · QA Q18	S_n = n + 2n^2; nth term divisible by 9	C
CAT 2019 Slot 1 · QA Q16	S_n = 3(2^(n+1) − 2); find a_11	6144

Part of Progressions & Series (38 questions since 2017).