Directions: Insert the missing number: 8, 7, 11, 12, 14, 17, 17, 22, (....)

### Concept & Logic The given series is a mixture of two alternating series. Series 1: $8, 11, 14, 17, \dots$ Series 2: $7, 12, 17, 22, \dots$ ### Step-by-Step Solution 1. Let's identify the pattern in each alternating series. 2. The first series is $8, 11, 14, 17, \dots$ The common difference is $+3$. 3. The second series is $7, 12, 17, 22, \dots$ The common difference is $+5$. 4. The missing number belongs to the first series, coming after 17. 5. Missing number $= 17 + 3 = 20$. ### Exam Strategy & Shortcut Whenever a series fluctuates (increases, then decreases, or increases irregularly), suspect an alternating series. Separate it into two (or sometimes three) sub-series by taking alternating terms. ### Common Pitfall Trying to find a single complex mathematical relationship between consecutive terms in an alternating series wastes time. Always check for alternating series first when the progression isn't smooth. ### Final Answer Therefore, the correct answer is **20**.