Difficulty: Easy
Correct Answer: 19 35
Explanation:
Introduction / Context:This series alternates two behaviors: an increasing subsequence and a fixed repeating value that appears at regular positions. Recognizing the period of the fixed term is key.
Given Data / Assumptions:
Concept / Approach:Note that every third term is 35, while the other terms form their own +2 progression across non-multiple-of-3 indices.
Step-by-Step Solution:
Positions and values: 1:3, 2:5, 3:35, 4:10, 5:12, 6:35, 7:17, 8:?, 9:?Every 3rd term is 35 (positions 3, 6, 9, …).The non-3rd positions increase by +2: 3→5→10→12→17→19 → …Thus, 8th term (not multiple of 3) = 17 + 2 = 19.9th term (multiple of 3) = 35.Verification / Alternative check:Check back: positions 1,2,4,5,7 follow +2 steps, and 3,6,9 are constant at 35. The pattern is fully consistent.
Why Other Options Are Wrong:
Common Pitfalls:Forgetting to check positional periodicity; not all patterns are simple differences—some embed a repeating constant at fixed intervals.
Final Answer:19 35
Discussion & Comments