3, 15, 35, 63….

Concept: This series is built from products of consecutive odd numbers — each term equals (2n − 1) × (2n + 1) for position n, i.e., the product of two consecutive odd integers that each increase by 2 from one term to the next.

1. 1st term: 1 × 3 = 3

2. 2nd term: 3 × 5 = 15

3. 3rd term: 5 × 7 = 35

4. 4th term: 7 × 9 = 63

5. 5th term (the value asked for): 9 × 11 = 99

Cross-check via differences: successive differences are 15 − 3 = 12, 35 − 15 = 20, 63 − 35 = 28 — each increasing by a constant 8. Extending this pattern, the next difference is 28 + 8 = 36, giving 63 + 36 = 99, which confirms the result.