5, 10, 6, 11, ?...?

Appeared in: MNS 2015

Explanation

The sequence is best understood as two independent, interleaved series.
Series 1 occupies the odd positions (1st, 3rd, 5th...) and follows the pattern: 5, 6, 7... (adding 1 each time).
Series 2 occupies the even positions (2nd, 4th, 6th...) and follows the pattern: 10, 11, 12... (also adding 1 each time).
Following this pattern, the numbers after 11 are 7 (from Series 1) and then 12 (from Series 2).
Since 7 is not an option, the correct answer is the next number in the sequence, which is 12.

Option B: This is incorrect. It does not fit the identified pattern of two interleaved series, each increasing by 1. For 13 to be the answer, the second series would have to follow a '10, 11, 13' sequence, which lacks a simple arithmetic rule.
Option C: This is incorrect. There is no consistent mathematical pattern (either interleaved or alternating) that would place 14 as the next number in the sequence.
Option D: This is incorrect. This would imply a large, inconsistent jump in the pattern. For example, in the alternating operation pattern (+5, -4), 15 does not fit.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Logical Reasoning: Number Series as background academic context rather than a clinical decision trigger.
While not a clinical question, this type of logical reasoning is a crucial skill for nurses.
Nurses use pattern recognition daily to interpret trends in vital signs, recognize the progression of a disease, identify adverse drug reactions, and perform accurate dosage calculations.
Strong analytical skills help in making sound clinical judgments and prioritizing patient care effectively.

How to Approach the Question

First, read the sequence carefully: 5, 10, 6, 11.
Look for a simple, single arithmetic pattern (e.g., addition, subtraction). Notice that the numbers go up, then down, then up, suggesting a more complex pattern.
Test for an alternating operation. 5 to 10 is +5. 10 to 6 is -4. 6 to 11 is +5. This reveals a consistent '+5, -4' pattern.
Alternatively, check for interleaved series. Examine the numbers in odd positions (1st, 3rd...): 5, 6. This is a simple '+1' series. Examine the numbers in even positions (2nd, 4th...): 10, 11. This is also a '+1' series.
Apply the identified pattern to find the next terms. The next odd-position term is 7 (6+1). The next even-position term is 12 (11+1).
The sequence continues as 7, 12. Compare this with the options. Since 7 is not an option but 12 is, select 12 as the answer.

Concept Tested & Keywords

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Practise the full MNS 2015

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