Find the missing term(?) in the following series.

1,6,3,8, 5, 7, 7, 12

Appeared in: NCL (MP) Nursing Officer - 2019

Explanation

The question presents a mixed or alternating number series.
There are two independent series interleaved within the main sequence.
The first series (at odd positions) is 1, 3, 5, 7, which follows a pattern of adding 2.
The second series (at even positions) is 6, 8, ?, 12. To maintain a consistent pattern, the missing number must be 10 (8 + 2 = 10, and 10 + 2 = 12).
Therefore, the missing term is 10.

Option B: If the missing term were 12, the second series would be 6, 8, 12, 12. The pattern would be +2, +4, +0, which is not a logical or consistent progression.
Option C: If the missing term were 16, the second series would be 6, 8, 16, 12. The pattern would be +2, +8, -4, which lacks a clear logical rule.
Option D: If the missing term were 6, the second series would be 6, 8, 6, 12. The pattern would be +2, -2, +6, which is inconsistent and does not follow a simple arithmetic rule.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain This question tests logical reasoning skills, specifically the ability to identify patterns in a number series as background academic context rather than a clinical decision trigger.
While not a clinical question, logical reasoning is a fundamental skill for nurses.
Nurses use pattern recognition and logical deduction daily to interpret patient symptoms, analyze lab data trends, and make critical decisions about care.
Strong reasoning skills help in prioritizing tasks, troubleshooting equipment, and anticipating patient needs, which are essential for patient safety and effective care.

How to Approach the Question

First, read the series carefully: 1, 6, 3, 8, 5, ?, 7, 12.
Attempt to find a single, simple pattern (e.g., addition, subtraction, multiplication) connecting all the numbers. You'll notice that no single rule applies.
When a single pattern fails, suspect an alternating or interleaved series. Write out the numbers in two separate lists by taking every other number.
Analyze the first sub-series (1, 3, 5, 7) to find its pattern. Here, the rule is to add 2.
Analyze the second sub-series (6, 8, ?, 12) to find its pattern. The most logical rule is also to add 2.
Apply the pattern to the second series to find the missing term: 8 + 2 = 10. Check if this fits the rest of the series: 10 + 2 = 12. It does.

Concept Tested & Keywords

Concept Tested: This question tests logical reasoning skills, specifically the ability to identify patterns in a number series.
Stem keywords: missing term, series, 1,6,3,8, 5, ?, 7, 12
Lead-in keywords: Find

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Attempt every question from this paper in a timed mock, then review the full solution for each one.