Question

Look at this series: 8, 43, 11, 41, _ _ , 39, 17, _ _ What number should fill in the blank?

• A. 13
• B. 15
• C. 14
• D. 16
• E. 40

Hint:

To identify alternating series, look for a "sawtooth" pattern where numbers increase then decrease repeatedly.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Check for an alternating series where two different mathematical rules are applied to odd and even positions.
Step 2: Identifying the Vector of Change:
- Pattern 1 (1st, 3rd, 5th...): 8, 11, \_\_, 17. The gap between 8 and 11 is $+3$. - Pattern 2 (2nd, 4th, 6th...): 43, 41, 39. The gap is $-2$.
Step 3: Calculation:
The blank is the 5th term, which belongs to Pattern 1. $11 + 3 = 14$. To verify, $14 + 3 = 17$, which matches the 7th term.
Step 4: Final Answer:
The missing number is 14. Thus, the correct option is (c).