NinetynineAP problems: write terms as a + (n − 1)d and solve
CAT has tested this idea 5 times across 4 papers, from 2017 to 2025. 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 2025 Slot 3 · QA Q2 | sum of 4th, 7th, 10th terms and S_14; find S_5 | 65 |
| CAT 2024 Slot 1 · QA Q14 | x_5 = −4 and a relation among four terms | B |
| CAT 2017 Slot 1 · QA Q31 | 7th term squared equals 3rd × 17th | A |
| CAT 2023 Slot 2 · QA Q20 | two APs with prime differences meeting at two terms | A |
| CAT 2017 Slot 1 · QA Q34 | sum of 3n terms gives n; compare with first n | B |
Part of Progressions & Series (38 questions since 2017).