Question

Look at this series: 7, 10, 8, 11, 9, 12, ... What number should come next?

• A. 7
• B. 10
• C. 13
• D. 11

Hint:

This series can also be viewed as two interleaved series:
- Odd positions: $7 \rightarrow 8 \rightarrow 9 \rightarrow 10$ (increases by 1)
- Even positions: $10 \rightarrow 11 \rightarrow 12$ (increases by 1)
The next term belongs to the odd series, which is $9 + 1 = 10$.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
To find the next number in a sequence, we must identify the mathematical pattern or rule governing the transition from one term to the next.
Detailed Explanation:
Let us analyze the differences between consecutive terms in the series:
- $7 \rightarrow 10$: Increase by 3 ($+3$)
- $10 \rightarrow 8$: Decrease by 2 ($-2$)
- $8 \rightarrow 11$: Increase by 3 ($+3$)
- $11 \rightarrow 9$: Decrease by 2 ($-2$)
- $9 \rightarrow 12$: Increase by 3 ($+3$)
The alternating pattern is $+3, -2, +3, -2, +3$.
Following this rule, the transition to the next term must be a decrease of 2 ($-2$):
- $12 - 2 = 10$

Step 2: Final Answer:
The next number in the series is 10, which corresponds to Option (B).