Question

How many odd digits are there in the following series of digits, each of which is immediately preceded by an even digit, but not immediately followed by an odd digit?
7 2 8 9 1 3 4 5 7 5 8 9 6 9 1 8 2 4 9 2 6

• A. 1
• B. 2
• C. 4
• D. 3
• E. 5

Hint:

Mark the "target" (odd numbers) first, then check the neighbor conditions to avoid missing any in a long string.

Answer 1

The Correct Option is D

Concept: Look for the pattern: Even Number $\rightarrow$ Odd Number $\rightarrow$ Even Number.
Scan the series for Even-Odd combinations. The sequence is: 7, 2, 8, \underline9, 1, 3, 4, \underline5, 7, 5, 8, \underline9, 6, \underline9, 1, 8, 2, 4, \underline9, 2, 6. Matches: 1. ...8, 9, 6... (Preceded by 8, followed by 6) 2. ...4, 9, 2... (Preceded by 4, followed by 2)